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Chapter 7

Chapter 7:  Skeletal System


I.  Bone Structure

A.  Bone Classification

1.  The four classes of bone according to shape are long, short, flat, and irregular.

2.  Examples of long bones are forearm and thigh bones.

3.  Short bones are shaped like cubes.

4.  Examples of short bones are wrist bones and ankle bones.

5.  Flat bones are platelike structures.

6.  Examples of flat bones are some skull bones, ribs, and scapulae.

7.  Irregular bones have a variety of shapes.

8.  Examples of irregular bones are vertebrae and some facial bones.

9.  Round bones are also called sesamoid bones.

10.  Sesamoid bones are small and nodular and embedded in tendons.

11.  An example of a sesamoid bone is the patella.

B.  Parts of a Long Bone

1.  An expanded end of a long bone is an epiphysis.

2.  An epiphysis articulates with another bone.

3.  Articular cartilage is located on an epiphysis.

4.  The shaft of a long bone is called a diaphysis.

5.  Periosteum is a tough, vascular, fibrous membrane covering the diaphysis of a bone.

6.  Periosteum functions to form and repair bone tissue.

7.  Processes provide sites for attachments of tendons or ligaments.

8.  The wall of the diaphysis is composed of compact bone.

9.  Compact bone has a continuous matrix with no gaps.

10.  The epiphyses are largely composed of spongy bone bone.

11.  Spongy bone consists of bony plates called trabeculae.

12.  A bone usually has both compact bone and spongy bone.

13.  A canal called the medullary cavity runs through the diaphysis.

14.  Endosteum lines the medullary cavity and spaces of spongy bone.

15.  Endosteum contains bone-forming cells.

16.  The tissue that fills the spaces of bone is called marrow.

17.  The two forms of marrow are red and yellow.

C.  Microscopic Structure

1.  Introduction

a.  Bone cells are called osteocytes.

b.  Lacunae are tiny, chambers that contain osteocytes.

c.  Lacunae form concentric canals around central canals.

d.  Osteoctyes transport nutrients and wastes to and from nearby cells.

e.  Cellular processes of osteocytes pass through canaliculi.

f.  The intercellular matrix of bone is composed of collagen and inorganic salts.

2.  Compact Bones

a.  An osteon is a cylinder-shaped unit of compact bone.

b.  The substance of compact bone is formed from many osteons cemented together.

c.  Each central canal contains blood vessels and nerves.

d.  Perforating canals connect osteons.

e.  Perforating canals contain larger blood vessels and nerves.

3.  Spongy Bone

a.  Spongy bone is also composed of osteocytes

and intercellular material.

b.  Unlike compact bone, the bone cells do not aggregate around central canals.

c.  Instead the cells lie within trabeculae.

d.  Osteocytes get nutrients from substances diffusing into canaliculi that lead to the surface of trabeculae.

II.  Bone Development and Growth

A.  Introduction

1.  Parts of the skeleton begin to form during the first few weeks of prenatal development.

2.  Bony structures continue to grow until adulthood.

3.  Bones form by replacing existing connective tissues.

4.  Intramembranous bones originate within sheetlike layers of connective tissue.

5.  Endochondral bones originate within cartilage.

B.  Intramembranous Bones

1.  Examples of intramembranous bones are flat bones of the skull.

2.  Osteogenesis is bone development.

3.  During their development, membranelike layers of primitive connective tissue appear at the sites of their future bones.

4.  Networks of blood vessels supply the connective tissue layers.

5.  Osteoblasts are bone-forming cells.

6.  Osteoblasts deposit bony matrix around themselves.

7.  Spongy bone can become compact bone as spaces fill with bone matrix.

8.  As development continues, osteoblasts may become surrounded by matrix.

9.  Matrix surrounding the processes of osteoblasts gives rise to canaliculi.

10.  Once isolated, osteoblasts become osteocytes.

11.  Periosteum comes from cells of the primitive connective tissue that persist outside of the developing bone.

12.  Compact bone is formed by osteoblasts on the inside of periosteum.

13.  Intramembranous ossification is the process of replacing connective tissue to form an intramembranous bone.

C.  Endochondral Bones

1.  Most of the bones of the skeleton are endochondral bones.

2.  Endochondral bones develop as masses of hyaline cartilage.

3.  Eventually the cartilage decomposes.

4.  As the cartilage decomposes, a periosteum forms from

  connective tissue that encircles the developing structure.

5.  Blood vessels and undifferentiated connective tissue cells invade the disintegrating tissue.

6.  Some of the cells differentiate into osteoblasts.

7.  Osteoblasts form spongy bone in the spaces previously housed by cartilage.

8.  Endochondral ossification is the process of forming an endochondral bone by the replacement of hyaline cartilage.

9.  The primary ossification center is an area in the diaphysis of a long bone in which the bony tissues begin to replace hyaline cartilage.

10.  Secondary ossification centers appear in epiphyses.

11.  The epiphyseal plate is a band of cartilage between the primary and secondary ossification centers.

D.  Growth at the Epiphyseal Plate

1.  In a long bone, the diaphysis is separated from the epiphysis by an epiphyseal plate.

2.  The cartilaginous cells occur in four layers.

3.  The first layer is composed of resting cells that do not actively participate in growth.

4.  The first layer anchors the epiphyseal plate to the bony tissue of the epiphysis.

5.  The second layer contains rows of many young cells undergoing mitosis.

6.  As new cells appear, the cartilaginous plate thickens.

7.  The third layer is formed by older cells that are left behind as new cells appear.

8.  The cells of the third layer enlarge and thicken the epiphyseal plate.

9.  The fourth layer is composed of dead cells and calcified intercellular substance.

10.  Osteoclasts break down calcified matrix of bone.

11.  Osteoclasts originate from monocytes.

12.  Osteoclasts secrete acids that dissolve the inorganic component of the calcified matrix, and their lysosomal enzymes digest the organic components.

13.  Osteoclasts phagocytize components of the bony matrix.

14.  After osteoclasts remove the matrix, osteoblasts invade the region and deposit bone tissue in place of calcified matrix.

15.  A long bone continues to lengthen while the cartilaginous cells of the epiphyseal plates are active.

16.  Lengthening of the bone is no longer possible when once the ossification centers of the diaphysis and epiphysis meet and the epiphyseal plates ossify.

17.  The medullary cavity forms when osteoclasts erode bone tissue in the diaphysis.

18.  The bone in the central regions of the epiphyses and diaphysis remains spongy. 

19.  Hyaline cartilage on the ends persists as articular cartilage.

E.  Homeostasis of Bone Tissue

1.  Throughout life, osteoclasts resorb bone tissue and osteoblasts replace bone.

2.  About 3% to 5% of bone calcium is exchanged each year.

F.  Factors Affecting Bone Development, Growth, and Repair

1.  Factors that affect bone development, growth and repair include nutrition, exposure to sunlight, hormonal secretions, and physical exercise.

2.  Vitamin D is necessary for calcium absorption.

3.  Lack of vitamin D can lead to the diseases rickets and osteomalacia.

4.  Vitamin A is necessary for osteoblast and osteoclast activity during normal development.

5.  Vitamin C is required for collagen synthesis.

6.  Growth hormone stimulates division of cartilage cells in epiphyseal plates.

7.  In children, the absence of growth hormone leads to pituitary dwarfism.

8.  An excess of growth hormone before the epiphyseal plates ossify leads to pituitary gigantism.

9.  In adults, an excess of growth hormone leads to acromegaly.

10.  Thyroid hormone can halt bone growth by causing premature ossification of the epiphyseal plates.

11.  Deficiency of thyroid hormone may stunt growth.

12.  Parathyroid hormone stimulates an increase in the number and activity of osteoclasts.

13.  Androgens are male sex hormones.

14.  Androgens promote formation of bone tissue.

15.  Sex hormones also stimulate ossification of the epiphyseal plates.

16.  Females typically reach their maximum heights earlier than males because the effects of estrogen on the epiphyseal plates are stronger than androgens.

17.  Physical stress stimulates bone growth.

III.  Bone Function

A.  Support and Protection

1.  Bones give shape to structures such as the head, face, thorax, and limbs.

2.  The bones of lower limbs, pelvis, and vertebral column support the bodys weight.

3.  The bones of the skull protect the eyes, ears, and brain.

4.  The bones of the thorax protect the heart and lungs.

5.  Bones of the pelvic girdle protect lower abdominal and internal reproductive organs.

B.  Body Movement

1.  Bones and muscles interact as levers.

2.  The four basic components of a lever system are rigid bar, fulcrum, object that is moved against resistance, and a force.

3.  In scissors, the handle and blades form a rigid bar.

4.  The pivot of scissors is the screw.

5.  The resistance of scissors is the material to be cut.

6.  The force of scissors is supplied by the person on the handles.

7.  In a first-class lever system, the parts are arranged resistance, fulcrum, force.

8.  Besides scissors, other examples of first class lever systems are seesaws and hemostats.

9.  In a second-class lever system, the parts are arranged fulcrum, resistance, force.

10.  An example of a second-class lever system is a wheelbarrow.

11.  In a third class lever system, the parts are arranged resistance, force, and fulcrum.

12.  An example of a third-class lever system is a pair of tweezers.

13.  In the action of bending the upper limb at the elbow, the rigid bar is the forearm bones, the pivot is the elbow joint, the resistance is the hand, and the force is applied by muscles on the anterior side of the arm.

14.  Bending the arm at the elbow is an example of a third-class lever system.

15.  When the upper limb straightens at the elbow, the rigid bar is forearm bones, the pivot is the elbow, the resistance is the hand, and the force is applied by the triceps muscle located on the posterior surface of the arm.

16.  Straightening the arm at the elbow is a first class lever system because   the parts of the lever are arranged resistance, pivot, force.

17.  An example of a second-class lever system in the body is a movement produced at the temporomandibular joint (opening of the mouth)

C.  Blood Cell Formation

1.  Hematopoiesis is blood cell formation.

2.  Blood cell formation begins in the yolk sac.

3.  Later in development, blood cells are made in the liver, the spleen, and red bone marrow.

4.  Marrow is a soft, netlike mass of connective tissue within the medullary cavities of bond bones, in the irregular spaces of spongy bone, and in the larger central canals of compact bone tissue.

5.  Red marrow functions in the formation of red blood cells, white blood cells, and platelets.

6.  Red marrow occupies the cavities of most bones in an infant.

7.  With increasing age, yellow marrow replaces red marrow.

8.  Yellow marrow stores fat.

9.  In an adult, red marrow is primarily found in the spongy bone of the skull, ribs, sternum, clavicles, vertebrae, and pelvis.

D.  Inorganic Salt Storage

1.  Intercellular matrix of bone tissue contains collagen and inorganic mineral salts.

2.  The salts account for about 70% by weight.

3.  Hydroxyapatites are tiny crystals of calcium phosphate.

4.  The body requires calcium for many metabolic processes including blood clot formation, nerve impulse conduction, and muscle cell contraction.

5.  When blood calcium is low, parathyroid hormone stimulates osteoclasts to break down bone tissue to release calcium salts.

6.  Very high blood calcium levels inhibit osteoclast activity.

7.  Calcitonin stimulates osteoblasts to form bones.

8.  Bone tissue contains lesser amounts of magnesium, sodium, potassium and carbonate ions.

IV.  Skeletal Organization

A.  Number of Bones

1.  The number of bones in a human skeleton is around 206.

2.  Flat bones of the skull are tightly joined by sutures.

B.  Divisions of the Skeleton

1.  Two major portions of the skeleton are axial and appendicular.

2.  The axial skeleton contains skull bones, middle ear bones, the hyoid bone, vertebral column bones, and thoracic cage bones.

3.  The skull is composed of 8 cranial bones and 14 facial bones.

4.  The hyoid bone supports the muscles of the tongue.

5.  The hyoid bone is located in the neck between the lower jaw and the larynx.

6.  The vertebral column consists of vertebrae, a sacrum, and coccyx.

7.  The distal end of the column is formed by the sacrum and the coccyx.

8.  The coccyx is also called the tailbone.

9.  The thoracic cage is composed of 24 ribs and the sternum.

10.  The appendicular skeleton consists of bones of the pectoral girdle, upper limbs, pelvic girdle, and lower limbs.

11.  The pectoral girdle is formed by scapulae and clavicles.

12.  The pectoral girdle connects the bones of the upper limb to the axial skeleton.

13.  The pectoral girdle aids in upper limb movements.

14.  Each upper limb consists of a humerus, radius, ulna, carpals, metacarpals, and phalanges.

15.  The humerus, radius, and ulna articulate at the elbow.

16.  The wrist bones are called carpals.

17.  The bones of the palm are called metacarpals.

18.  Bones in the fingers are called phalanges.

19.  The pelvic girdle is formed by coxal bones.

20.  The pelvic girdle connects the bones of the lower limbs to the axial skeleton.

21.  The pelvic girdle, sacrum, and coccyx form the pelvis.

22.  Each lower limb consists of a femur, tibia, fibula, patella, tarsals, metatarsals, and phalanges.

23.  The femur and tibia articulate with each other at the knee.

24.  The kneecap is called the patella.

25.  The anklebones are tarsals.

26.  The bones of the instep of the foot are called metatarsals.

27.  Bones of the toes are called phalanges.

V.  Skull

A.  Introduction

1.  A human skull usually consists of 28 bones.

2.  The moveable bone in the skull is the mandible.

3.  Some cranial and skull bones together form the orbit of the eye.

B.  Cranium

1.  The cranium encloses and protects the brain.

2.  The surface of the cranium provides attachments for muscles that make chewing and movements of the head possible.

3.  Sinuses are air-filled cavities in cranial bones.

4.  Sinuses reduce the weight of the skull and increase the intensity of the voice by serving as resonant sound chambers.

5.  The eight bones of the cranium are 1 frontal bone, 2 parietal bones, 1 occipital bone, 2 temporal bones, 1 sphenoid bone and 1 ethmoid bone.

6.  The frontal bone forms the anterior portion of the skull above the eyes, the roof of the nasal cavity and the roofs of the orbits.

7.  The supraorbital foramen is on the upper margin of each orbit and allows blood vessels and nerves to pass to tissues of the head.

8.  The sinuses of the frontal bone are called frontal sinuses.

9.  The two halves of the frontal bone fuse together by the fifth of sixth year of life.

10.  One parietal bone is located on each side of the skull behind the frontal bone.

11.  Together the parietal bones form the sides and roof of the cranium.

12.  The sagittal suture fuses the parietal bones.

13.  The coronal suture fuses the parietal bones to coronal bones.

14.  The occipital bone joins the parietal bones along the lambdoidal suture.

15.  The occipital bone forms the back of the skull and the base of the cranium.

16.  The foramen magnum is a large opening in the occipital bone through which the brain and spinal cord join.

17.  Occipital condyles are located on each side of the foramen magnum.

18.  Occipital condyles articulate with the first cervical vertebra.

19.  A temporal bone on each side of the skull joins the parietal bone along a squamosal suture.

20.  The temporal bones form parts of the sides and the base of the cranium.

21.  The opening leading inward to parts of the ear is called the external auditory meatus.

22.  Mandibular fossae articulate with condyles of the mandibles.

23.  The mastoid process is a site of attachment for certain muscles of the neck.

24. The styloid process is a site of attachment for muscles of the tongue and pharynx.

25.  The carotid canal is near the mastoid process and transmits the internal carotid artery.

26.  The jugular foramen is opening between the temporal and occipital bones and accommodates the internal jugular vein.

27.  The zygomatic process projects anteriorly from the temporal bone and joins the zygomatic bone.

28.  The sphenoid bone helps form the anterior portion of the cranium.

29.  The sella turcica is an indention in the middle of the sphenoid bone and holds the pituitary gland.

30.  The sinuses of the sphenoid bone are called sphenoidal sinuses.

31.  The ethmoid bone is located in front of the sphenoid bone.

32.  It consists of two masses joined by cribiform plates.

33.  The cribiform plates form the roof of the nasal cavity.

34.  Nerves associated with smell pass through olfactory foramina.

35.  Portions of the ethmoid bone also form section of the cranial floor, orbital walls, and nasal cavity walls.

36.  A perpendicular plate projects downward from the cribiform plates to form most of the nasal septum.

37.  Scroll-shaped plates called superior and middle nasal conchae project inward from the lateral portions of the ethmoid bone.

38.  The lateral portions of the ethmoid bone contain many small air spaces called ethmoidal sinuses.

39.  The crista galli is triangular process that projects upward and is located between cribiform plates.

40.  The crista galli is attached to membranes that enclose the brain.

C. Facial Skeleton

1.  The facial skeleton consists of 13 immovable bones and a movable lower jaw bone.

2.  The facial bones provide sites of attachment for muscles that move the jaw and control facial expression.

3.  The maxillary bones form the upper jaw.

4.  Portions of the maxillary bones also comprise the anterior roof of the mouth, the floors of the orbits, and sides and floor of the nasal cavity.

5.  The maxillary bones also contain sockets for the upper teeth.

6.  Inside the maxillae, lateral to the nasal cavity are maxillary sinuses.

7.  The maxillary sinuses extend from the floor of the orbits to the roots of the upper teeth.

8.  During development, portions of the maxillary bones called palatine processes grow together and form the anterior section of the hard palate.

9.  The alveolar arch is a horseshoe shaped collection of alveolar processes.

10.  Teeth occupy cavities in this arch.

11.  The palatine bones are L shaped.

12.  The palatine bones are located behind the maxillae.

13.  The horizontal portions of the palatine bones form the posterior section of the hard palate and the floor of the nasal cavity.

14.  The perpendicular portions of the palatine bones help form the lateral walls of the nasal cavity.

15.  Zygomatic bones are responsible for the prominences of the cheeks below and to the sides of the eyes.

16.  Each zygomatic bone has a temporal process that extends posteriorly to join the temporal bone.

17.  The zygomatic arch is formed by the zygomatic process of the temporal bone and the temporal process of the zygomatic bone.

18.  Lacrimal bones are located in the medial wall of each orbit.

19.  The nasal bones form the bridge of the nose.

20.  The nasal bones are attachments for the cartilaginous tissues that form the shape of the nose.

21. The vomer is located along the midline within the nasal cavity.

22.  Posteriorly the vomer joins the perpendicular plate of the ethmoid bone.

23.  The nasal septum is formed from the vomer and perpendicular plate of the ethmoid.

24.  The inferior nasal conchae are attached to the lateral walls of the nasal cavity.

25.  Like the ethmoidal conchae, the inferior conchae support mucous membranes within the nasal cavity.

26.  The mandible is shaped like a horseshoe.

27.  The flat projections at the ends of a mandible are rami.

28.  The rami are divided into a mandiblar condyle and a coronoid process.

29.  The mandibular condyles articulate with the temporal bones.

30.  The coronoid processes provide attachment sites for muscles used in chewing.

31.  The alveolar border is a curved bar of bone on the superior border of the mandible and it contains the sockets of the lower teeth.

32.  Mandibular foramens are located near the center of each ramus.

33.  Blood vessels and nerves run through mandibular foramens.

34.  The mental foramen is an opening near the point of the jaw.

D.  Infantile Skull

1.  At birth, the skull is incompletely developed with fibrous membranes connecting the cranial bones.

2.  Fontanels are membranous areas of an infantile skull.

3.  Fontanels permit some movement between the bones so that the developing skull is partially compressible and can slightly change shape.

4.  Eventually fontanels close and cranial bones grows together.

VI.  Vertebral Column

A.  Introduction

1.   The verterbral column extends from the skull to the pelvis and forms the vertical axis of the skeleton.

2.  The vertebral column is composed of vertebrae that are separated by intervertebral discs.

3.  The vertebral column supports the head and the trunk of the body.

4.  The vertebral column protects the spinal cord.

5.  The spinal cord passes through a vertebral canal.

6.  An infant has 33 separate bones in the vertebral column

7.  The sacrum is formed by five fused vertebrae.

8.  The coccyx is formed by four fused vertebrae.

9.  An adult vertebral column has 26 bones.

10.  The four curvatures of the vertebral column are thoracic, pelvic, cervical, and lumbar.

11.  The cervical curvature develops when a baby begins to hold up its head.

12.  The lumbar curvature develops when a child begins to stand.

B.  A Typical Vertebra

1.  The body of a vertebra forms the thick, anterior portion of the bone.

2.  The intervertebral discs are fastened to the upper and lower surfaces of the vertebral bodies.

3.  The discs cushion and soften the forces caused by walking and jumping movements.

4.  Anterior longitudinal ligaments join the bodies of adjacent vertebrae on their anterior surfaces.

5.  Posterior longitudinal ligaments join the bodies of adjacent vertebrae on their posterior surfaces.

6.  Pedicles are two short stalks that project posteriorly from each vertebral body.

7.  Laminae are two plates that arise from the pedicles and fuse in the back to become spinous processes.

8.  A vertebral arch formed by the pedicles, laminae, and spinous processes.

9.  Spinous processes are structures formed by the fusion of two laminae.

10.  A transverse process projects laterally and posteriorly.

11.  Superior and inferior articulating processes project upward and downward from each vertebral arch.

12.  Intervertebral foramina provide passageways for spinal nerves.

C.  Cervical Vertebra

1.  There are 7 cervical vertebrae.

2.  The transverse processes of cervical vertebrae are distinctive because they have transverse foramina.

3.  The spinous processes of the second through the sixth cervical vertebrae are bifid.

4.  The vertebra prominens is the spinous process of the 7th cervical vertebra.

5.  The atlas is the 1st cervical vertebra.

6.  The atlas supports the head.

7.  The facets of the atlas articulate with occipital condyles.

8.  The axis is the second cervical vertebra.

9.  The dens is a process that projects upward and lies in the ring of the atlas.

10.  As the head is turned from side to side, the atlas pivots around the dens.

D.  Thoracic Vertebra

1.  There are 12 thoracic vertebrae.

2.  The facets of thoracic vertebrae articulate with ribs.

3.  The bodies of thoracic vertebrae are adapted to bear increasing loads of body weight.

E.  Lumbar Vertebra

1.  There are 5 lumbar vertebrae and they are located in the small of the back.

2.  The bodies of lumbar vertebrae are larger and stronger than the superior vertebrae.

3.  The transverse processes of lumbar vertebrae project posteriorly and the spinous processes are thick, short, and nearly horizontal.

F.  Sacrum

1.  The sacrum is triangular in shape.

2.  The median sacral crest is ridge of tubercles where the spinous process of sacral vertebrae fused together.

3.  Dorsal sacral foramina are rows of openings located to the sides of the tubercles.

4.  The sacrum is wedged between the caxae and is united to them at its articular surfaces.

5.  The sacrum forms the posterior wall of the pelvis

6.  The sacral promontory is upper anterior margin of the sacrum.

7.  Anterior sacral foramina provide passageways for nerves and blood vessels.

G.  Coccyx

1.  The coccyx is the lowest part of vertebral column.

2.  Sitting presses on the coccyx, and it moves forward, acting like a shock absorber.

VII.  Thoracic Cage

A.  Introduction

1.  The thoracic cage includes the ribs, thoracic vertebrae, the sternum, and the costal cartilages that attach the ribs to the sternum.

2.  The thoracic cage supports the shoulder girdle and upper limb and protects the viscera in the thoracic and upper abdominal cavities.

B.  Ribs

1.  The usual number of ribs is 24.

 2.  The true ribs are the first 7 pairs of ribs.

3.  The false ribs are the last five pairs of ribs.

4.  Floating ribs are the last two pairs of false ribs.

5.  A typical rib has a long, slender shaft.

6.  The head of a rib is an enlarged portion of a rib at its posterior end.

7.  The head of a rib articulates with a facet on the body of its own vertebra and with the body f the next higher vertebra.

8.  A tubercle of a rib articulates with the transverse process of the vertebra.

9.  Costal cartilages are composed of hyaline cartilage.

10.  Costal cartilages are attached to the anterior ends of a rib.

C.  Sternum

1.  The sternum is located along the midline in the anterior portion of the thoracic cage.

2.  The three parts of the sternum are manubrium, body, and xiphoid process.

3.  The xiphoid process projects downward.

4.  The manubrium articulates with clavicles.

5.  The manubrium and body articulate with ribs.

VIII.  Pectoral Girdle

A.  Introduction

1.  The four parts of the pectoral girdle are two clavicles and two scapulae.

2.  The pectoral girdle supports the upper limbs and is an attachment for several muscles that move the arm.

B.  Clavicles

1.  A clavicle has an S shape.

2.  Clavicles run between the sternum and the shoulders.

3.  The medial ends of the clavicles articulate with the manubrium.

4.  The lateral ends of the clavicles articulate with the scapulae.

5.  The clavicles brace the freely movable scapulae and are attachment sites for muscles of the upper limbs, chest and back.

C.  Scapulae

1.  The scapulae are shaped like triangles.

2.  The spine of a scapula divides it into a supraspinous process and infraspinous process.

3.  The acromion process forms the tip of the shoulder.

4.  The coracoid process curves anteriorly and inferiorly to the clavicle.

5.  The acromion process articulates with the clavicle.

6.  The glenoid cavity is a depression on the head of a scapula.

7.  The glenoid cavity articulates with the head of the humerus.

8.  The three borders of the scapulae are superior, lateral, and medial.

IX.  Upper Limb

A.  Introduction

1.  The bones of the upper limb form the framework for the arm, forearm, wrist and hand.

2.  The bones of the upper limbs are humerus, radius, ulna, carpals, metacarpals, and phalanges.

B.  Humerus

1.  The humerus extends from the scapula to the elbow.

2.  The head of the humerus fits into the glenoid cavity.

3.  Two processes just below the head are a greater tubercle and lesser tubercle.

4.  The intertubercular groove is a furrow between the greater tubercle and lesser tubercle.

5.  The anatomical neck is the narrow depression along the lower amrgin of the heard that separates it from the tubercles.

6.  The surgical neck is a tapering region just below the head and the tubercles of the humerus.

7.  The deltoid tuberosity is an attachment site for the deltoid muscle.

8.  Two condyles at the lower end of the humerus are the capitulum and trochlear.

9.  The capitulum is on the lateral side and articulates with radius.

10.  The trochlea is on the medial side and articulates with the ulna.

11.  Epicondyles are located above the condyles and provide attachments for muscles and ligaments of the elbow.

12.  The coronoid fossa is a depression between the epicondyles anteriorly that receives the coronoid process of the ulna when the arm bends at the elbow.

13.  The olecranon fossa is a depression on the posterior distal surface of the humerus that receives the olecranon process of the ulna when the arm straightens at the elbow.

C.  Radius

1.  The radius is located on the thumb side of the forearm

2.  The radius extends from the elbow to the wrist and crosses over the ulna when the hand is turned so that the palm faces backward.

3.  The head of the radius articulates with the capitulum of the humerus.

4.  The radial tuberosity is an attachment site for the biceps brachii.

5.  The styloid process is located at the distal end of the radius on its lateral side.

D.  Ulna

1.  The trochlear notch of the ulna is a wrenchlike opening at the proximal end of the ulna.

2.  The trochlear notch articulates with the trochlea of the humerus.

3.  The olecranon process is located above the trochlear notch.

4.  The head of the ulna articulates with laterally with a notch of the radius and with a disc of fibrocartilage inferiorly.

5.  The styloid process of the ulna is located at the distal end of the ulna on its medial side.

E.  Wrist and Hand

1.  The wrist is at the junction of the forearm and the hand.

2.  The bones of the wrist are called carpals.

3.  The individual names of the 8 carpals are scaphoid, capitate, trapezoid, trapezium, lunate, hamate, triquetrum, and pisiform.

4.  The anterior surface of the wrist is concave to allow for the passage of tendons and nerves into the palms.

5.  The hand is composed of a palm and five fingers.

6.  The metacarpals form the framework of the palm.

7.  The distal ends of metacarpals form the knuckles of a clenched fist.

8.  Proximally, the metacarpals articulate with carpals.

9.  Distally, the metacarpals articulate with phalanges.

10.  The metacarpal of the thumb is numbered 1.

11.  The finger bones are phalanges.

12.  Each finger has 3 phalanges and the thumb has 2 phalanges.

X.  Pelvic Girdle

A.  Introduction

1.  The pelvic girdle consists of two coxae that articulate with each other anteriorly and with the sacrum posteriorly.

2.  The pelvis is formed by the sacrum, coccyx, and pelvic girdle.

3.  The pelvic girdle supports the trunk of the body.

4.  The pelvic girdle provides attachments for the lower limbs and protects the urinary bladder, the distal end of the large intestine, and the internal reproductive organs.

5.  The bodys weight is transmitted through the pelvic girdle to the lower limbs and then onto the ground.

XI.  Lower Limb

A.  Introduction

1.  The bones of the lower limb form the framework of the thigh, leg, ankle, and foot.

2.  The bones of the lower limb are the femur, tibia, fibula, patella, tarsals, metatarsals, and phalanges.

B.  Femur

1.  The femur extends from the hip to the knee.

2.  The head of the femur projects medially into the acetabulum.

3.  The fovea capitis is a pit marks the attachment of a ligament.

4.  The neck of the femur is a constriction just below the head.

5.  Two large processes below the neck of the femur are the greater and lesser trochanters.

6.  The linea aspera is a longitudinal crest on the posterior surface of the femur.

7.  The lateral and medial condyles articulate with the tibia.

8.  The patella articulates with the femur on its distal anterior surface.

9.  The medial and lateral epicondyles provide attachments for muscles and ligaments.

C.  Patella

1.  The patella is a sesamoid bone located in a tendon that passes anteriorly over the knee.

2.  The patella controls the angle at which this tendon continues toward the tibia.

D.  Tibia

1.  The shinbone is the tibia.

2.  The tibia is located on the medial side.

3.  The medial and lateral condyles of the tibia articulate with the condyles of the femur.

4.  The tibial tuberosity is located below the condyles of the tibia.

5.  The tibial tuberosity provides an attachment for the patellar ligament.

6.  The anterior crest of the tibia is a prominence that extends downward from the tibial tuberosity and attaches connective tissues in the leg.

7.  The medial malleolus is a prominence at the distal end of the tibia.

8.  On the tibias lateral side is a depression that articulates with the fibula.

9.  The inferior surface of the tibias distal end articulates with the talus.

E.  Fibula

1.  The fibula is on the lateral side of the tibia.

2.  The head of the fibula articulates with the tibia.

3.  The lateral malleolus articulates with the ankle.

F.  Ankle and Foot

1.  The ankle and foot consist of a tarsus, a metatarsus, and phalanges.

2.  The tarsus is composed of seven tarsal bones.

3.  The talus articulates with the tibia and fibula and can move freely at the ankle.

4.  The seven tarsal bones are the calcaneous, the talus, the navicular, the cuboid, and the lateral, medial, and intermediate cuneiform bones.

5.  The largest talus is the calcaneous.

6.  The calcaneous helps support the weight of the body.

7.  The metatarsus consists of five elongated bones.

8.  The heads at the distal ends of the metatarsals form the ball of the foot.

9.  The arch of the foot is formed by the arrangements of the tarsals and metatarsals.

10.  The bones of the toes are called phalanges.

11.  Each toes has 3 phalanges except the great toe because it lacks the middle phalynx.

XII.  Life-Span Changes

A.  An incremental decrease in height begins at about age 30.

B.  Compression fractures of the vertebrae may contribute to loss of height.

C.  As calcium levels fall, bones become brittle and prone to fracture.

D.  Gradually, osteoclasts come to outnumber osteoblasts.

E.  By age 35 all adults start to lose bone mass.

F.  Trabecular bone shows signs of aging first.

G.  Compact bone loss begins around the age of 40.

H.  In the first decade following menopause 15 to 20% of trabecular bone is lost and 10 to 15% of compact bone is lost in women.

I.  The most common fractures in the elderly are vertebral compression fractures, hip fractures, wrist fractures, leg fractures, and pelvis fractures.

J.  Preserving skeletal health may involve avoiding falls, taking calcium supplements, getting enough vitamin D, avoiding carbonated beverages, and getting regular exercise.


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