Anatomy & Physiology

Subtopic:

The Skeletal System

Contents

Learning Objectives

  • Understand the structure and function of the skeletal system.

  • Identify and classify types of bones and their anatomical features.

  • Describe the development, growth, and healing processes of bone tissue.

  • Explain the role of bone cells (osteoblasts, osteoclasts, osteocytes, osteogenic cells).

  • Compare compact vs. spongy bone structure and function.

  • Recognize the bones of the axial and appendicular skeleton.

  • Distinguish between male and female skeletal differences.

  • Describe the structure and function of joints, including types and movements.

  • Understand the influence of hormones, diet, and exercise on bone health.

  • Identify bones of the skull, vertebral column, thoracic cage, and limbs.

Introduction to Skeletal system

    • The human skeleton begins as cartilage and fibrous membranes. By age 25, the skeleton is completely hardened. The adult skeleton consists of 206 bones, which are 20% of body mass:
      • 80 bones in the axial skeleton.
      • 126 bones in the appendicular skeleton.
    • The skeletal system includes bones and structures connecting them to other tissues, such as ligaments, tendons, and cartilages.
    • A skeleton (the word skeleton came from a Greek word skeleton meaning “dried up”
    • It’s strong yet light adopted for its function of body protection and motion.
    • The skeletal system includes bones, cartilages, joints and ligaments. The joints give the body flexibility and allow movements to occur but from structural point of view the human skeleton consists of two main types of supportive connective tissue hat is bone and Cartilage.

Functions of the skeletal system

  • Shape/frame work, Protection, Support, Flexibility
  • Movement
  • Storage
  • Blood cell formation
  • Forming boundaries
  • Support: It forms the internal frame work that supports and anchors soft organs.
  • Protection: Bones protect soft body organs.
  • Movement: Skeletal muscles attached to the skeletal system use the bones to move the body and its parts.
  • Storage: Fats, blood cells are stored in the internal cavities of bones. It is also a store house of minerals e.g calcium and phosphate.
  • Blood cell formation: It occurs within the bone marrow cavities of long bones.

Bone

  • A bone/osseous is a specialized connective tissue that has the strength of cat iron and the lightness of pine wood.
  • Living bone is not dry, brittle or dead. It is a moist, changing, productive tissue that is continually resorbed, reformed and remolded.

Types of Bones

  • Long bone: femur, tibia, fibula
  • Short bone: carpals. (Wrist)
  • Flat bone: ribs, sternum
  • Sesamoid bone: patella (Knee cap, pisform carpel bone
  • Irregular bones: vertebrae, some skull bones.

BONE STRUCTURE

  • It has the Diaphysis and two epiphysis or extremities. The Diaphysis is composed of compact bone and a hollow cyclindrical walls containing (filled-with) yellow bone marrow. The epiphysis consists of an outer covering of compact bone with spongy or cancellous bone inside.
  • The two parts are separated by epiphyseal /cartilage which ossify when growth is complete
  • Long bones are almost completely covered by a vascular membrane the periosteum which has two layers. The outer layer is tough and fibrous, and protects the bone underneath.
  • The inner layer contains osteoblasts (bone cells) and osteoclasts responsible for bone production and break down, and is important in repair and remolding of the bone.
  • The periosteum covers the whole bone except the parts that form the joints where it is replaced by articular/bone cartilages.

BONE TISSUE

  • It is composed of cells embedded in the matrix of ground substance or fibres.
  • It is more rigid than other tissues because it contains organic salts mainly calcium phosphate and calcium carbonate. Cap04 & caco3. A net work of collagenous fibres in the matrix  gives bone tissue ,its strength  and flexibility.
  • Most bones have an outer sheath of compact bone tissue enclosing an interior spongy bone tissue.

COMPACT BONE TISSUE

  • It is found in the outer sheath of the bone. It is very hard and dense. It appears to a naked eye to be solid but is not. It contains cylinders of calcified cells called Osteon (Harversian system).
  • Osteons are made of concentric layers called lamellae which are arranged seemingly in a wider and wider seeming straws.
  • In the center of the osteons are central canal (Haversian canal) which is longitudinal canals that contain blood vessels, nerves, and lymphatic vessels.
  •  Central canals usually have canals called perforating canals that run at right and to the central canal extending the system \of nerves and vessels out ward to periosteum.

LACUNAE. (Little spaces)

  • These house bone cells ( osteocytes) and  are contained  in the lamellae radiating  from each  lacuna are tiny  canaliculi  connecting  (osteocytes) where  nutrients and wastes  can pass  to and  from the  central canal.

SPONGY (CANCELLOUS) BONE

  • It looks like a honey comb using the naked eye. Microcopic examination reveals a frame work formed from trabeculae, meaning little beams.  Trabeculae are tiny spikes of bone tissue sorounded by bone matrix that are calicified.
  •  The spaces between the trubeculae contain Redbone marrow in addition spongy bone is lighter than compact bone reducing the weight of the skeleton.

DEVELOPMENT OF A BONE TISSUE

  • This is called ossification or osteogenesis. This begins before birth and is not complete until about the 21 year of life.
  • Long, short and irregular bones develop in the feotus from rods of cartilage (cartilage model).
  • Flat bones develop from membrane model. Ribs, stemum sesamoid bones from tendon model eg Patella.
  • During the process of bone development, osteoblasts secrete osteoid which gradually replaces the initial model. This osteoid is progressively calcified, as the bone grows the osteoblasts mature and become osteocytes.

Diagram

In mature bone, definite balance of osteoblast and osteoclast activity maintains normal bone structure. If osteoclast activity exceeds osteoblast activity, the bone becomes weaker.  On the other hand, if osteoblast activity outstrips osteoclast activity, the bone becomes stronger and heavier.

DEVELOPMENT OF LONG BONES

  • In long bones the focal points from which ossification begins are small areas of osteogenic cells or centers of ossification in the cartilage model.  This is accompanied by development of a bone collar at about 8 weeks of gestation.
  • Later the blood supply develops and bone tissue replaces cartilage as osteoblasts secrete osteoid in the shaft.  The bone lengthens as ossification continues and spreads to the epiphyses. Around birth, \secondly centers of ossification develop in the epiphyses, and the medullary canal forms when osteoclasts break down the central bone tissue in the middle of the shaft.  During childhood, long bones continue to lengthen because the epiphyseal plate at each end of the bone, which is made of cartilage, continues to produce new cartilage on is diaphyseal surface (the surface facing the shaft of the bone).
  • This cartilage is then turned to bone.  As long as cartilage production matches the rate of ossification, the bone continues to lengthen, at puberty, under the influence of sex hormones, the epiphyseal plate growth slows down and is overtaken by bone deposition. Once the whole epiphyseal plate is turned to bone, no further lengthening of the bone is possible.

Hormonal regulation of bone growth

 Hormones that regulate the growth, size and shape of bones include the following.

growth hormone and the thyroid hormones, thyroxine and tri- iodothyronine, are especially important during infancy and child hood; deficient or excessive secretion of these results in abnormal development of the skeleton.

Testosterone & estrogens influence the physical changes that occur at puberty and help maintain bone structure throughout life.  Rising levels of these hormones are responsible of the epithyseal plates.  So that bone growth length ways stops (although bones can grow in thickness throughout life. Average adult male height is usually greater than female, because male puberty tends to occur at a later age than female puberty, giving a male child bone longer to keep growing. Oestrogens are responsible for the wider female pelvis that develops during puberty, and maintaining bone mass in adult female. Falling estrogen levels after menopause can put postmenopausal women at higher risk of bone fracture (osteoporosis).

Calcitonin & parathyroid hormone

 Control blood levels of calcium by regulating its uptake into and release from bone. Calcitonin increases calcium uptake into bone (reducing blood calcium), and parathemone decreases it (increasing blood calcium). Although the length and shape  of bones  does not  normally  change after   ossification  is complete,  bone  tissue is  continually  being remoulded  and replaced  when  damaged.  Osteoblasts continue to lay down osteoid and osteoclasts reabsorb it. The rate in different bone varies eg the distal part of the femur is replaced over a period of 5 to 6 months.

Exercise and bone

 Although bone growth lengthways permanently ceases once the epiphyseal plate have ossified, thickening of bone is possible throughout life.  This involves the laying down of new osteons  at the periphery  of the bones through  the action of osteoblasts  in the inne r layer of  the periosteum. Weight bearing exercise stimulates thickening of bone, strenghthening it and making it less liable to fracture. Lack of exercise reverses the changes, leading to lighter, weaker bones.

Diet & bone

Healthy  bone tissue  requires  adequate  dietary  calcium  and vitamins A, C, and D calcium and smaller  amounts of  other minerals such as phosphate, iron,  and manganesium, is essential for adequate  mineralization  of bone.  Vitamin A is needed for osteoblast activity. Vitamin C is used in collagen synthesis and vitamin D is required for calcium and phosphate absorption  from the  intestinal tract.

BONE MARKINGS

Most bones have rough surfaces, raised protuberances and ridges that give attachment to muscle tendons and ligaments.  These are not included in the following  descriptions  of individual  bones unless  they are of  particular  note, but many  are  marked  on illustrations.  Bone makings and related terminology are defined in table.

Anatomical terminology related to bones.

  • Terms                                     meaning
  • Articulating surface: The part of the bone that enters into the formation of a joint 
  • Articulation:  A joint between two or more bones.
  • Bony sinus:  A hollow cavity within bone.
  • Border:  A ridge of bone separating two surfaces.
  • Condyle: A smooth rounded projection of bone that forms part
  • of a joint.
  • Facet: A small, generally rather flat, articulating surface.
  •  cleft: A narrow slit
  • Foramen (Plural: Foramina); A hole in a structure.
  • Fossa (Plural: Fossae);  A hollow or depression.
  • Meatus: A tube – shaped cavity within a bone.
  • Septum: A partition separating two cavities.
  • Spinous process or crest: a sharp ridge of bone. Styloid processes, a sharp downward projection of bone that gives attachment to muscles and ligaments.
  • Suture; An immovable joint eg; between the bones of the skull.
  • Trochanter, tuberosity;        Roughened bony projections, usually for attachment of muscles or ligaments. The different names are used according to the size to the size of the projection. Trochanters are the largest and tubercles  the smallest.

BONE CELLS

 The bone contains 5 types of cells

Osteogenic cells: These are small spindle shaped cells. They are found mostly in the deepest layer of periosteum. They have a high mitotic potential and can be transformed into bone forming cells. (Osteoblasts).

Osteoblasts (Bone farming cells): These are bone forming cells. They secrete both organic and inorganic components of the bone. (Calcium phosphate)

They are found in places;

  • In the deeper layers of periosteum
  • In the centre of ossification of immature bone.
  • At the ends of the diaphysis adjacent to the epiphyseal cartilage of the long bone.
  • At the site of a fracture

Osteocytes: Are the main cells of fully developed cells mature bone cells? They have a cell that occupies the lacuna Osteocytes are derived from osteoblasts. They monitor and maintain bone tissue.  They are nourished by tissue fluid in the canaliculi that radiate from the central canal.

 Osteoclasts: These are multi nuclear giant cells which are found where bone is resorbed during its normal growth (resorption of bone tissue). Osteoclasts are derived   from white blood cells called monocytes. They are mainly found under the periosteum to maintain the shape of bones during growth and to remove excess callus formed  during healing of fractures.

HEALING OF BONE

 There are a number of terms used to classify bone fractures including: –

  1. SIMPLE: The bone ends do not protrude through the skin 
  2. COMPOUND: The bone ends protrude through the skin.
  3. PATHOLOGICAL: Fracture of a bone weakened by disease.

Following a fracture, the broken ends of bone are joined by the deposition of new bone. This occurs in several stages.

  • A haematoma – (collection of clotted blood) forms between the ends of bone and in surrounding oft tissues.
  • There follows development of acute inflammations and accumulation of inflammatory exodate, containing macrophages that phagocytose the haematoma and small dead fragments of bone (this takes about 5 days) Fibroblasts migrate to the site, granulation tissue and new capillaries develop.
  • New bone forms as large numbers of osteoblasts secrete spongy bone which unites the broken ends and is protected by an outer layer of bone and cartilage, the new deposits of bone and cartilage is- called a callus. Over the next few weeks, the callus matures, and the cartilage is gradually replaced with new bone.
  • Reshaping of the bone continues and gradually the medullary canal is reopened through the callus (in weeks or months). In time the bone heals completely with the callus tissue completely replaced with mature compact bone. Often the bone is thicker and stronger the repair site than originally, and a second  fracture  is more likely  to occur at  a different 
  • The adult human skeleton has 206 names bones that are grouped into two principal parts.
  • The axial and appendicular skeleton:
  • The axial skeleton consists of bones that lie around the axis they include skull, vertebral column, ribs, sternum. Together the bones forming these structures constitute the centre core of the body (the axis).
  • The appendicular skeleton consists of bone of the body out of the axial group. These are the appendages/attachments. It consists of: the shoulder girdle with upper limbs, the pelvic girdle with lower limbs.

SKULL

It has 29 bones. It is dividing into two parts. The Skull  rests  on the upper  end of the  vertebral  column and  its bony  structure  is divided into  two parts  the cranium  and the face.

The bones of the skull and their suture:

CRANIUM

  • The cranium is formed by a number of that and irregular bones that provide a bony protection to the brain.
  • It has a base upon which the brain rest and covers the brain.
  • The periosteum lining the inner surface of the skull bones forms the outer layer of the diameter.
  • In a mature skull the joints (sutures) between the bones are immovable (fibrous).
  • The bones of the cranium are eight in number and include: 2 parietal bones, 2 temporal bones , 1 Ethimoid bone,  1 Sphenoid bone,  1 Ocupital bone, 1 frontal bone

FRONTAL BONE

  •  This is the bone of the forehead. It forms part of the orbital cavities/eye sockets) and prominent rides above the eyes called the (supraorbital margins).
  • Just above the supraorbital margins within the bone cavities (sinuses) lined with epithelial mucus membrane and this opens into the nosal cavity.
  •  The coronal suture joins the frontal bone to the two parietal bones.

PARIETAL BONES

 These bones from the sides and roof of the skull:  They articulate with each other at the sagittal suture with the frontal bone at the coronal suture with the occipital bone at the lambdoidal suture and on the  temporal  bone at  the squamous suture.

The inner surface is concave and is grounded, to accommodate the brain and blood vessels.

TEMPORAL BONES

  • These lie on each side of the head. They articulate with the parietal, occipital and sphenoid and zygomatic bone.
  • The squamous part; It is a thin f shaped area that articulate with the parietal bones.
  • The zygomatic process; It articulates with zygomatic bone to form the zygomatic arch (cheek bone)
  • The temporal bone articulates with the mandate at the temporomandibular joint: The only movable joint of the skull.

OCCIPITAL BONE

 This bone forms the back of the heard and part of the base of the skull. It has immovable joints between the parietal, temporal and sphenoid bones, its inner is deeply concave and this concavity is occupied by the parts of the brain called cerebrum. The occipital bone has two articular condyles that form condyloid joint with the first bone of the vertebral column called atlas. This joints permits nodding movement of the head.  Between the condyles is the faramen magnum (large hole) through which the spinal cord passes into the cranial cavity.

SPHENOID BONE

This bone the middle portion of the base of the skull and it articulates with the occipital, temporal parietal and frontal bones. On the superior surface in the middle of the bone is a little saddle shaped depression, the hypophyseal fossa where the pituitary gland is found. This bone contains fairly large air sinuses lined with ciliated mucus membrane which open into the nosal cavity.

ETHMOID BONE

It occupies the anterior part of the base of the skull and helps to form the orbital cavity, the nasal septum and the lateral walls of the nasal cavity.  It is a very delicate bone containing many air sinuses. The horizontal flattened part (the cribriform plate) forms the roof of the nasal cavity and has numerous small foramina through which  nerve  fibres of the olfactory  nerve (sense of  smell) pass upwards from the  nosal cavity  to the  brain.

FACE

face :13 bones from the face; 2 Zygomatic (check bones), 1 maxilla, 2 nosal bones, 2 lacrimal bones, 1 vomer, 2 palatine bones, 2 inferior conchae , 1 mandible

ZYGOMATIC (check bones)

  • They originate as two bones that fuse before birth. They form the prominences of the checks, part of the floor and lateral walls of the orbital cavities.

MAXILLA (upper jaw bone)

  • They originate as two  bones but fusion  takes place  before  birth.  It forms  the upper jaw,  the anterior  part  of the roof  of the mouth,  the lateral  walls of  the nosal  cavity  and part of  the floor of orbital cavities.
  • The alveolar  ridge  or process  carries  the upper  teeth  and on each  sides it contains air  sinuses  ( the  maxillary sinus).

NASAL BONES

There are two small  flat  bones that form  the  greater  part of the  lateral  and superior  surface  of the ridge of  the nose.

LACRIMAL BONES: There  two small  bones  posterior and lateral  to  the nosal  bones  and form  part of the  medial  walls  of the  orbital cavities.  Each is pierced by a foramen  for the  passage  of the nasal lacrimal dust that carries the tears  from the  eyes to the nosal cavity.

VOMER: The  vomer bone is  a thin flat bone that  extends  upwards  from the middle  of the hard palate  to form  most of the inferior  part of the  nasal  septum.

PALATINE BONES: They are two L-shape bones. The horizontal  part  unite  to form  the posterior  part of the  hard palate  and the  perpendicular  parts  project  upwards  to form  part  of the lateral  walls of the nasal cavity.

INFERIOR CONCHAE: Each concha is a scroll – shaped bone, which forms part of the lateral wall of the nasal  cavity.  The superior and middle conchaa are parts of the ethmoid bone. The conchae  collectively  increase  the surface  area in the  nasal  cavity  allowing  inspired air to  be warmed  and humidified  more effectively.

MANDIBLE (lower jaw bone): It is the only movable bone of the skull they originate as two but unite at the middline  before birth.  Each half consists of two main parts;

  • A curved body with alveolar ridge containing the lower teeth.
  • This projects upwards at right angles  to  the posterior  ends of the body.

The condylar process which articulates with the temporal bone to form the temporomandibular  joint.

The coronoid process which gives attachment to  moscles and ligaments  that closes the jaw. The point where the ramus joins the body is the angle of the jaw.

Diagram

HYOD BONE : It is an isolated horse shoe- shaped bone lying in the soft tissues of the neck just above the larynx and below the mandible.

It does not articulate with any other bone, but is attached to the styloid process of the temporal bone by ligaments. It supports the larynx and gives attachment to the base of the tongue.

SINUSES

  • They air filled cavities found in the sphenoid, ethmoid, maxilla and frontal bone.
  • They all communicate with the nasal cavity and are aligned with ciliated mucus membrane.
  • They give resonance to the voice and reduce weight of the skull.

FONTANELLES FO THE SKULL

These  are membraneous  areas  where two  or three  sutures meet. The two largest  are the : Anterior  fontanelle  and Posterior  fontanelle. The anterior  fontanelle is not fully ossified  until the  child is  12-18 months old and the  fontanelle  usually  is ossified  two to three months  after birth.  The skull does not fuse earlier to allow for moulding  of the  babies head during  child birth.

Functions of the skull
  • The cranium protects  the delicate tissues  of the brain.
  • The bone eye sockets  provide  the eye  with protection against  injury  and give  attachment  to the muscles  that  move the 
  • The temporal bone protects  the delicate  structures of  the ear.
  • The sinuses in some face  and skull  give  resonance to the  body and  keep the skull  weight in a minimum.
  • The maxilla and the  mandible  provide alveolar ridges  in which  the teeth  are embedded.
  • Chewing of food is performed by the  mandible  controlled  by muscles  of the lower 

THE VERTEBRAL COLUMN

  1.  The human  vertebral column (back one) or spine  of the human  skeleton  consisting  of 24 articulating verterbra and a fusal vertebra in the sacrum  and coecyx.
  2. The vertebia column protects the spinal  cord. They are normally 33 vertebra.
  3. The upper 24 are articulating  and separated  from each  other by  the intervetebra discuss and  the lower   are fused  in adults,  five in the sacrum  and  in the  coccyx. (tailbone).

Characteristics of a typical vertebra

 It must have a body and neural arch.

BODY

  • It is broad flattened largest   part of the vertebra.
  • It is the flatteted  surfaces  of the body  of each vertebra  that articulates  with corresponding  surfaces  of adjacent  verterbia.
  • No direct contact of the vertebra. There is  a tough pad of fibrocartilage  called  intervertebral discs.
  • Bodies  of the vertebra  lie to the  front of  the vertebral column increasing  greatly  in size  towards  the base of  the spine  as the lower spine  has  to support  much  weight  than the upper part.

VERTEBRAL (NEURAL) ARCH

  • This encloses  a large  vertebra foramina. It lies  behind  the body,  forming  posterior  and lateral  walls of lateral  foramina. Lateral walls  are formed  from plates of bones called pedicles  and the posterior walls are  formed from lamina.
  •  Projecting  from the  region  where the  pedicles  meet the  lamina  is the  transverse  processes and where  the two  lamina meet  at the back  is the process  called the  spinous  process. These prominences  can be felt  through the  skin along the  length  of the spine. The vertebral  foramen  form  the vertebral  neural  canal  that  contains  the spinal cord.

Diagram

THE CERVICAL VERTEBRA (Vertebra)

  • They are the smallest  vertebra. the transverse processes  have a farmen through which  the vertebral artery  passes  up to  the brain. It has  vertebra. The first  two cervical  vertebra  are; Atlas & Axis.
  • The first cervical  vertebra is  the Atlast  and is the bone where the skull  rests. The second  cervical  bone is the axis  where  the skull  turns. The atlas  has some short  traverse process.
  • It posses 2 flattened  facets that  articulate  with the occipital bone to  form a joint that  permits  nodding  of the head.

Axis : The axis  sits below the  atlas  and has  a small body with a superior  projection  called for  odontoid process also  called dens (tooth).  This occupies part of the  posterior  foramen of the  atlas and  its  held  secretly  by the  transuense  ligaments. The head  pivots (turns side to  side( on this joint. The seventh cervical  vertebrae  is the  vertebra prominens which  is easily  felt  at the  base of the neck.

LUMBAR VERTEBRA: It’s the largest  of the vertebra. This is  because they  have to support  the weight  of the upper body, They have  substancial  spinous  processes  for attachment  of  muscles  of the lower back.

Diagram

SACRUM: It consists of 5 rudimentary  fused vertebra which forms a triangular  or wedge  shaped  bone with  a concave  anterior  surface.

The upper  part or base  articulates  with the fifth lumber vertebra on each side  it articulates  with the illium  to form the sacroiliac joint. The inferior  part  articulates  with eh  coccyx.

The anterior  edge of the base (promotary) protrudes  into the pelvic cavity. It has vertebra  foramina for the passage  of blood vessels and nerves.

COCCYX: It consists of four (4) fused terminal vertebra to  form  a very small  triangular  bone. The broad base articulates with the  tip of the  sacrum.

FEATURES OF THE VERTEBRA COLUMN

 Intervertebral discs

  • Bodies  of adjacent  vertebral  are separated  by intervetebral  discs  consisting  of fibro cartilage.
  • thinnest  in the  cervical  and progressively  thicker  towards the lumbar  region as spinal loading increases.
  • They are kept  in place by the posterior  longitudinal  ligament.
  • They act  as shock  absorbers.
  • Fibrocartilage  form  cartilaginous  joint which  contribute to  flexibility  of the vertebra  column  as a whole.

 Intervertebral foramen

When the vertebra are viewed   seen from a side  aforamen  formed  by the gap between  the pedicles  can be seen.

 There is intervertebra foramina on each side  between  every pair  of vertebri through  which the  spinal nerves,  blood vessels  and lymph  vessels.

Ligaments of the vertebia column

These hold  the vertebia together  and keep  the cartilaginous  joint in position.

Transverse  ligaments

  •  The transverse keep  the ondotoid  process in correct  position  in relation  to atlas.
  • Anterior  longitudinal  ligament: The moves  the whole length  of the vertebral  column and  lies infront of the  vertebra.
  • Posterior longitudinal  ligament: This lies inside the  vertebral  canal  and in close contact  with the posterior  surface  of the bodies of the  vertebra.
  • Supra spinous  ligament : This connect  the spinous process from the occinut to the sacrum.

Curves of the vertebra

When viewed from the side  the vertebra column presents for  curves. Two primary, and Two secondary curves; The fetus in the uterus  lies curved  so that  the  head and  knees  are more less toughing this shows the  primary  curvature. When a child can hold up his head ( after  about 3 months).

The first  secondary  cervical  curve develops. And when a child  can stand up right  (around 12-15 months) the second   any lumber  curve. The thoracic and sacral curvature is maintained  hence the two  primary curves. Primary curves : Thoracic ,  and Socral

Secondary  curves:  Cervical  (1st), Lumbar (2nd)

Movement of the  vertebral  column

  • Movement between bones  of the vertebra is limited  some  movements  include:-
  • Flexion (bending forward)
  • Extension (bending backward)
  • Lateral  flexion (bending aside)
  • Rotation (turning  round)

NB More movement  is in cervical  and lumbar  region.

function  of the  vertebral  column

  • The vertebral  canal gives  strong  protection  for the delicate  spinal cord.
  • The intervertebral  foramina  provides  passage  for spinal nerves,  blood vessels,  lymph  vessels.
  • The supports  the skull
  • Intervertebral  discs  act as shock absorbers  protecting the  brain.
  • It forms  the axis  of the trunk giving attachment  for ribs, shoulder, girdle and limbs, pelvic girdle  and lower limbs.
  • The numerous individual  bones  with other intervebral discs  allow movement of  the whole column.

THORAX

  •  This refers  to the chest.
  • It is a bony cage formed by  sternum, ribs, coastal  cartilage , bodies  of the thoracic  vertebra.

STERUM (Breast  bone):

It is a flat narrow  born measuring  about 15cm (6 inch) located  in the median  line of the  anterior  thoracic wall. It consists of three basic portions

  • The manubrium (superior  portion)
  • The body (middle and largest  portion)
  • Xiphoid  process  (inferior and smallest  portion)

The junction of the manubrium  and the body  forms  the sterna  angle.The manubrium on its superior portion  has a  depression  called Jugular (suprasternal  notch). On each side  of the jugular  notch  are clavicular  notch that articulates with  first and  second  ribs. The body of the  sternum  articulates  directly  or indirectly with the 2nd to 10th rib.

The xiphoid process  consists  of hyaline cartilage  during  infancy and  childhood and do not  ossify  completely up-to the age of 40.

Diagram

RIBS

  • Human being  contain 12 pairs of  ribs  that make up  the side of the  thoracic cavity.
  • Ribs  increase  in length  from  1st  to the 7th and they  decrease  in length  to the 12th .
  • Each rib  posteriorly  articulates  with the body of  its corresponding thoracic vertebra.
  • Anterioly the first of ribs  have direct  attachment  to sternum  by coastal  cartilage  hence  they  are called  true ribs  (vertebra-sternal  ribs)
  • The remaining  three  ribs are  called false ribs. The 8th, 9th, 10th ribs  are the false  ribs (vertebral- chondrial ribs) because their  cartilage  attach  one another  and then  attach  their cartilage  to the 7th rib.
  • The 11th and 12th ribs  are disgnated as floating  ribs  because their  anterior part  doesn’t even attach  tough  indirectly  to the sternum.

Diagram

APPENDICULAR  SKELETON

It consists  of the shoulder  girdle  and the pelvic girdle.

The shoulder girdles and upper  limbs: 2 upper  limbs ( extremities), 2 clavide collar bone), 2 scapulae  humerous (1), Radius (1), ulna(1) wrist (caupal) (8),  metacarpal s (5), phalanges (14_. Total 32 bones.

  • The lower  limbs  consists  of  the femur (s), fibula (1), tibia (1) , Patella (1), Tarsal (7), metatarsal (s) phallnges (15) total 30 bones
  • Two innominate  bones (2)
  • The total  bones of  the appendicular  skeleton  are 128 bones.
  • The pelvic  girdle  has two innominate  bones  consisting  of the illium,  ischium,  and pubis.

SHOULDER  GIRDLE (Pectoral)

Clavicle  (collar  bone)

They are two in number.

  • Double curved long bone with rounded medial end and flattened lateral bone. It isS-shaped.
    It is  held in place by ligaments
  • It holds  shoulder joints  and arm away from the  thorax  so that  the upper  limb can  swing freely.
  • It articulates  with the  manubrium of the sternum at  the sternol- clavicular joint and  also articulates with the  acromion  process of  the scapula  to farm the acromic- clavicular joint.
  • It allows  the upper  arm to  move freely.
  • It is the only attachment/bony link  of the appendicular  skeleton  to the axial skeleton.

Scapula/shoulder  blade

They are  two in number

  • It is a flat  triangular  bone with  a horizontal  spine  separating fossa.  It is a site for attachment of the muscles of the arm.
  • At the lateral  angel  is a shallow  articular surface the  glenoid cavity which articulates  with the  head  of the humerous to form  the shoulder  joint.
  • The prominence  which can be  felt  through the skin is called  the acromion process which articulates with the  claucle  to  form acromio  clavicular  joint. (Synoval joint).
  • A slight  movable  joint that  contributes  to the mobility  of  the shoulder  girdle. It has  also the coracoid rocess  for attachment  of  muscles  of the shoulder.

Diagram

Humerous

They are two in number.

  • It is the longest  bone of the upper limb.
  • It forms ball and  socket joint  with the  glenoid fossea of the scapula.
  • It is a site  of attachment  of muscles  of the shoulder and arm permitting  the arm  to flex, extend.
  • At the distal and of the head  are two  roughened projections of the bone  that is , greater  and lesser tubercles and in between  them is a deep groove Bicipital  glove. (intertubercular sulcus). This is occupied by the tendon of the biceps muscle. At the  distal end of the  bone presents  two round/smooth  surfaces  which articulate with  the Radius and Ulna to form the elbow joint.

Diagram

Fore arm (Ulna & Radius)

Shoulder girdle

  • It is composed  of two  bones  i.e. Radius and Ulna. Radius is larger  of the two bones. But ulna  is longer . Ulna  has olacranon  process which  is the prominence of elbow. The two  bone  articulates  with the  humerous  at the  elbow  to form elbow  joint.
  • Wrist joint: The two  bones  articulate  with each other at the  proximal  end to form. Radio ulna joint.

Wrist (carpel bones)

They are firmly  held together  by ligaments  that  allow  little or  slight movement  between  them. The bones  of the proximal  low form  part of the  wrist joint  while  those of the distal row articulate  with the  metacarpal  bones  forming  distal  carpal metacarpular  joint.

Palm (Metacarpel) bones

  • They are five bones  in each side.
  • They are  numbered  from the  thumb  side in wards.
  • The proximal  end articulates  with the  carpel bone forming  carpal  metarcapular joint.
  • Carpal metarcapular  joint.

Function

The joint  aid in cupping  of the hand.

Phalanges

They are  14 in number and they  articulate with each  other at  the interphalangeal joint and  this allows  fingers  to participate  in stable  grips.

Diagram

PELVIC GIRDLE

 It is formed by two  innominate hip  bones.  Pelvis  is the  term  given to the basin  shaped structure  formed  by the  two innominate bone , sacrum and coccyx.

 Innominate bones

  • These are  formed by three fused  bones  that is:- Illium, ischium, publis
  • On it is lateral  surface,  it has a depression  which is  the  acetabulum which articulates  with head  of the femur to form  Hip joint.

Ilium: articulates with the  sacrum 

Upper flattened  part of the  bone which  presents the iliac crest. It forms  the synovial joint with the  sacrum (sacro-iliac joint ). A strong joint  capable of absorbing  stressed  of  body weight.

  1. It tends to become  fibrosed  in latter  life.

Pubis

  • It is the  anterior part of the  bone.
  • It articulates with  each other  at a  cartilaginous joint,  the symphysis pubis.

Ischium

  • This forms  the inferior  and posterior  part of  the bone.  It presents  with rough  inferior  projections,  the ischial  tuberosities which bear the weight  of the body  when  seated.

PELVIS

  • It is divided  into  upper and  lower parts . (Brim of the pelvis). It consists  of : prometary  of the sacrum.
  • Ileopectineal  line.
  • The greater  or false  pelvis is above  the brim  and lesser  or true  pelvis is below the  brim.

Difference between male and female  pelvis

Male                                                               Female

  • Bones  are heavier                             Bones  are lighter
  • Pelvis is smaller                                 Pelvis is wider
  • Triangular shaped                             Rectangular shaped
  • Less shallower                                    More shallow
  • Triangular shaped                             Rounded
  • Not roomier                                        Roomier generally

 The shape  of the female  pelvis  allows  for the passage  of the  baby during  child birth.

Thigh/FEMUR BONE

  • This is a typical long bone
  • It is the longest, strongest, heaviest bone.
  • It  has  a spherical  head  that articulates  with the acetabulum  of  the hip bone to form  the hip joint  which is  a Ball & Socket Joint. It  has greater  and lesser trochanter for attachment  of  muscles.
  • At the lower extremities  it  has two condyles that is  Medial  and lateral  condlles  which  with tibia  and patella  form  the knee joint
  • Function:  To support the body.

Leg/TIBIA & FIBULA

  • Tibia which participates in forming both the knee and ankle joints.
  • At the  proximal  end presents  two condyles  for articulation  with the  femur  to form  the knee joint.
  • The head of  the tibula  articulates with the  inferior  aspect of  the lateral  condyle  of the Tibia  bone farming  proximal  tibiofibula  joint.
  • At the distal  and the Tibia  forms  the  ankle joint with  the falus and fibula.

Fibula:

  • It is a long slender  lateral  bone of the leg.
  • Its head articulates  with the lateral  condyle  of the  tibia  to form the  proximal  tibiofibula  joint and the  lower extremely  articulates  with the  tibia and projects  beyond  it to form  the lateral  malleolus.
  • This helps to stabilize  the ankle joint.

Diagram 

Arches of  the foot

  • Medial longitudinal arch
  • Trasverse arch
  • Lateral longitudinal  arch
  • The foot is supported by  three  arches  that  distribute  body weight  to the heel  and ball  of the foot.
  • Avoid damage  of blood vessels  and nerves
  • Increase  on stability.

Patella (knee cap)

  • It is a roughly triangular  shaped sesmoid bone associated  with the knee joint.
  • Its posterior surface articulates  with the patellar surface of the knee  joint  and its anterior  surface  is in the  patella, tendon, i.e. the tendon  of the quardriceps famoris muscle.

Tarsal (ankle) bones

  • The seven tarsal  bones  forming the  posterior  part of  the foot ( ankle) and three cuneiform  bones.  The talus  articulates with the tibia  and fibula  at the ankle joint. The calcaneus forms the heel  of the foot. The other  bones  articulate  with each  other  and with  the metatarsal bones.

Metatarsal (bones  of the foot)

  • They are five bones,  numbered from  inside out, which  form the greater  part of the  dorsum (sole) of the foot. At  their proximal  ends they  articulate  with the  tarsal  bones  and at the distal end with  the phalanges.  The  enlarged  distal head  of the 1st  metatarsal  bone forms the ball of the  foot.

Phalanges  (toe bones)

  • They are 14 phalanges arranged in a similar  manner  to those in the fingers ie
  • Two in the great  toe ( the hallux)
  • Three in  each of the  other toes.

Arches  of the foot

  • The arrangement  of bones in the  foot, supported by  associated  ligaments  and action of associated  muscles,  gives  the sole  of the foot  an arched  or curved  shape.  The curve  running from  head to  toe  is called  the longitudinal  arch and the curve  cross  the foot is  called the  transverse arch.

Questions

1)Identify the bones forming the appendicular skeleton.

  • State  the characteristics of bones  forming the  appendicular  skeleton.
  • Outline the differences  in structures  between the male and female pelvis

2) State  the functions  of bones

  • List  five types  of bones and  give an example  of each.
  • Outline  the general  structure  of along bone.
  • Describe  the structure  of compact and  spongy  bone tissue
  • Describe  the  development  of  bone.
  • Explain  the process of  bone healing and the  factors  that complicate it.
  • Outline the factors that determine  bone growth.

3) Identify  the  bones  of the skull ( face and  cranium)

  • List  the functions  of the sinuses and  fontanelles  of the  skull.
  • Outline  the characteristics  of a typical  vertebra.
  • Describe  the structure  of the  vertebral  column.
  • Explain  the movements  and functions  of the vertebral column.
  • Identify  the bones  forming  the thoraric cage.

JOINTS

Draw all necessary diagrams

Classification of joints

  • FIBROUS JOINTS: These are made of fibrous connective  tissue  which  unites  articulating  bones. There is  no joint cavity, Mostly are immovable and some are slightly movable.
  • Examples; Cranial sutures, Inferior  tibio fibula joint, Interosseus  ligament , Roots  of teeth  in Alveolar processes  of mandible  and maxilla.

CARTILAGENOUS JOINTS

  •  The articulating bones are united by a plate  of hyaline  cartilage  or fibrocartilage nous  disc mostly  slightly  movable  but some  immovable.
  • Examples; Symphysis pubis , Intervertebral  disc

SYNOVIAL JOINTS

  • Articulating bones  move freely  along smooth lubricated  articular  cartilage  which is  enclosed  within  a flex capsule.

Diagram

CHARACTERISTIC OF SYNOVIAL JOINTS

 Articular/hyaline cartilage

  • This provides  smooth  articular surface  forces  and bear  the weight  of the body.
  • Its about  7mm thick  in young people  and becomes thinner  and less compressible  with age  and thus  increase  stress on the  other  structures  of the bone.
  • Cartilage has no blood  supply. It only receives its nourishment from synovial fluid.

Capsular ligament

  • It is a sleeve  of fibrous  tissue  which  holds  bones  together. Its loose to allow freedom of moment  but strong enough to  protect  it from any injury.

Synovial membrane

  • It has epithelial  layer  which  lines the  capsule  and it secrets  synovial  fluid.

Synovial  fluid

It is a thick sticky  fluid  of egg  white consistence  that fill  the synovial  cavity.

Functions  of synovial fluid

  • Maintains bone structure.
  • Nourishes structures  within the cavity.
  • It contains  phagocytes which remove  microbes  and cellular  debris.
  • Acts as a  lubricant
  • Maintains  joint stability
  • Prevents ends of  bones from being  separated  does  a little water  btn  the glasses.
  • Some little sacs of synoval  fluid (bursae) are present  in some joints  eg the  knee  joint  and they  act as  cushions to  prevent  friction between  abone  and aligament  or tendon or skin  where the  bone is  near the surface.
  • Extra capsular structures: Examples:- tendons , Ligaments , Muscles , Nerve  and blood supply
  • The blood  and nerve  supply is  usually to the capsule  and to muscles  that move it.

Movement  possible  at synovial joint.

  • Flexion (bending  usually forward
  • Extension (straightening or bending backwards)
  • Abduction (movement  away from  the midline of the  body)
  • Adduction (movement  towards  the  midline)
  • Circumduction (movement  of the limb or  digit  so that  it  describes  the shape  of a cone.
  • Rotation (Movement along  the axis of above)
  • Pronation (turning  the palm  of the hand upwards)
  • Supination (Turning  the side of the foot inwards)
  • Inversion ( turning  the sole  of the foot inwards)
  • Eversion  (Turning  the sole  of the foot outwards)

TYPES OF SYNOVIAL JOINTS

1)Ball and socket joint

  • The head of  one bone  is ball shaped and  articulates  with a cup shaped  socket of  another.
  • It allows for  a wide  range  of movement like  extension, flexion,  abduction, abduction
  • Examples  include; Shoulder  joint , Hip joint

2) Hinge Joint

Articulating  ends  of the bones  form  an arrangement  like a hinge on a door and movement  is restricted  to extension and flexion  eg Elbow  joint. Interphalangaeal joint, Knee joint

3) Gliding joints : Articular  surfaces  are that  or very slightly  curved and glind  over one  another  but movement  is restricted. Its  the only  least  movable  joint of  the synovial joint.

Examples ; Joints  between the  carpal  bones in the  wrist, Tarsal  bones in the foot.

4)Pivot joint:  Allow  a bone or  limb to rotate.

Example; The head rotates  on the  pivot joint  formed by  the dens  of the axis  held  within the ring of the atlas  by transverse ligament  and  the ondotoid process  of the axis.

  • Candyloid joints: A condyle  is a smooth  rounded  projection  on a bone  and in a condyloid    It sits  within  a cupshaped  depression  on the other bone. Eg – A joint btn the  condyle  process of  the mandible and the temporal bone, Btn metacarpal  and phalanges , Metatarsal  and phalonges of the foot.

5) Saddle  joint: The articulating bones  fit together  like a man  sitting on  a saddle.

Example- Base of the thumb between  the trapezium to the wrist bones and  the first metacarpal bones.

  1. Ability to touch each of the finger tips on the  same hand  is due  to the nature  of the thumb  joint.

SHOULDER JOINT

  • It is a ball and socket joint.
  • It is the most movable/mobile in the body  and  least stable  and therefore easily  to dislocation especially in children
  • It is formed  by glenoid  cavity of the scapula  and the head  of the humerous  and is well  padded  with a  protective  bursae.
  • Glenoid cavity  is deepened by  a rim  of fibro  cartilage  and is called Glenoidal  labrum which provides  additional stability  without  limiting movement.
  • The joint  is stabilized  by a number  of ligaments ie Gleno humeral transverse. Also muscles with their  tendons

This is formed  by Trochlea and capitulum of the  humerous  then trochlear notch  of the ulna  and head of the  radius. Its extremely a stable joint because the humeral and ulna surfaces interalock and  the capsule  is strong. It has anterior, posterior, medial and lateral  strengthening  ligaments  for stability.

Diagrams

Proximal and distal  radioulnar joints

  • It is a pivot  joint (proximal radioulnar joint) and distal.
  • It is formed by  the rim of  the head of the radius rotating  in the radial  notch  of the ulna.
  • It forms  the same- capsule  as the  elbow  joint.
  • The annular  ligament  is a strong extra capsular  ligament  that encircles  the head of  the radius  and keeps it  in contact with  the radial  notch of the   ulna.
  • The interasseous membrane (fibrous membrane) links the bones  along their shafts  and prevents  separation  of the bones  when force is  applied  at either  end  ie at  the wrist  or elbow.

Muscles  and movements

  • The fore arm may be pronated (turned palm  down) or supinated  (turned  palm up)
  • Pronation  is caused by  the action of the  pronator  teres , supination  is by action of  supinator and biceps  muscles.

Wrist joint

  • It is a condyloid  joint formed  between  the distal end of the  radius  and the proximal end of the proximal  carpals,  ie the  scaphoid,  lunate  and friquetrum.
  • A disc of  white  fibrocartilage  separates  the ulna  from the joint  cavity and articulates with the  carpal  bones. It also  seperates  the inferior  radiolnar  joint from  the wrist joint.
  • Extracapsular  structures  consist  of medial  and lateral  ligaments  and anterior  and posterior radiocorpal ligaments.
  • It can be  flexed,  extended,  abducted,  adducted.

Diagram

Joints  of the  hands and fingers

  1. There are synovial joints between the  carpal  bones, between the  carpal  and metacarpal  bones,  between the  metacarpal  bones and  proximal  phalanges  and between the  phalanges.
  2. Movement of  the joints  of the hand and fingers is controlled by  muscles  in the fore arm  and smaller  muscles  within  the hand.  There are no muscles  in the fingers,  finger  movements are produced by  tendons  extending  from muscles  in the fore arm  and the hand.
  3. The joint of the base of  athumb is a saddle joint  unlike the corresponding  joints of  the other fingers, which are condyloid. This means  that the thumb  is more mobile  than  the fingers  and the  thumb can be flexed, extended circumducted, adbucted and adducted. In addition  the  palm can  be moved  across the palm  to touch  the tips of  each of the  fingers  on the same hand (opposition),  giving  great  manual  dexterity  and allowing  eg the holding  of a pen and the fine manipulation  of objects  held in the hand.
  4. The joints  between the  metacarpals  and finger  bones  allow  movement of the  fingers. The fingers  may be  flexed,  extended  adducted, abducted  and circumducted  with the first finger  more flexible  joints  (interphallangeal joints) are hinge joint  and allow  flexion  and extension.

HIP JOINTS

  • It is a ball and socket joint
  • It is formed by  the cup- shaped  acetabulum  of the  innominate (hip) bone and  the almost  spherical head  of the femur.
  • The capsular ligament encloses the head and most of the neck  of the femur.
  • The cavity is  deepened  by the  acetabulum labrum, a ring of  fibro-cartilage  attached to  the rim of the  acetabulum  which stabilizes  the joint  without  limiting  its range of  movement.
  • It is a steady and powerful joint, since it bears all  body weight  when standing. It is stabilized by  its  muscuclature,  but its  ligaments  are also  important.
  • The three main external  ligaments  are; Iliofemoral, Pubofemoral, Ischiofemoral

KNEE JOINT

  • This is the  body’s largest  and most complex  joint .
  • It is  a hinge joint formed y  the candyles  of the femur,  the tibia  condyles  and the posterior surface  of the patella.
  • The anterior part of  the capsule  is formed by the  tendon  of the quadriceps  femoris  muscle  which also  supports  the patella.
  • Intracapsular  structures include ; Two cruciate ligaments ,  Semilunar  cartilages (menisci)
  • Two cruciate ligaments that cross each other, extending from the  intercondylar notch of the femur to the intercondlar  eminence  of the tibia.  They help to stabilize the joint.
  • Semilunar  cartilages or Menisci  are incomplete discs  of  fibrocartilage  lying on  top of the  articular  condyles  of the  tibia. They are wedge shaped,  being  thicker                                                                                                                                                                                            at their  outer  edges and provide  stability.  They prevent  lateral  displacement  of bones  and cushion  the moving  joint by  shifting  within  the joint  space  according  to the relative  positions of the articulating  bones. Bursae  and pads  of fat are numerous. They prevent friction between a bone and aligament  or tendon  between  the skin  and the  patella.
  • Synovial  membrane covers  the cruciate  ligaments  and  the pads  of fat.  The menisci are not  covered with  synovial  membrane because they are weight  bearing.
  • External  ligaments  provide  further  support,  making it a  hard joint  to dislocate.
  • Movements at this joint  are:- flexion  extension  and  a rotary movement  that ‘locks” the joint  when fully  extended.
  • When the  joint is locked  it is possible  to stand  upright  for long period  of time without tiring  the knee  extensions.
  • Muscles extending the knee:-Quadriceps femoris, Principal flexors; Gastocnemius, Hamstrings
ANKLE JOINT
  •  It is a hinge joint.
  • It is formed by  the distal end of the  tibia  and its Mallelus (Medial Malleolus), the distal  end at the fibula  lateral malleolus  and the tallus.
  • Four important ligaments strengthen  this joint.
  • Deltoid and the anterior, Posterior, Medial ,Lateral
  • Movements of inversion  and eversion occur between the  tarsal bones and not the ankle  joint movements.

Diagram

JOINTS OF THE FEET AND TOES

 There are a number of synovial joints between the tarsal  bones.

  • Between the tarsal  bones and  metatarsal  bones.
  • Btn the metatarsals and proximal phalanges.
  • Between the phalanges.

Movements are  produced by  muscles  in the leg  with long  tendons that cross the  ankle  joint and  by muscles of the foot. The tendons crossing the ankle  joint are wrapped  in synovial  sheaths  and held  close to the  bones by strong transverse ligaments.

They move smoothly  within their sheaths  as the joints move. In addition  to moving  the joints  of the first,  these  muscles  support  the arches  of the foot  and help  to maintain  balance.

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