THE SKELETAL SYSTEM - THE AXIAL

SKELETON

GROSS ANATOMY

Chapter 8

Anatomy and Physiology Lecture

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APPENDICULAR SKELETON

Appendicular Skeleton includes bones of the A. Pectoral Girdles (shoulder); B. Pelvic Girdles (Hip); C. Upper Extremities; and D. Lower Extremities.

PECTORAL (SHOULDER) GIRDLE

-Attach the bones of the Upper Extremities to the Axial Skeleton. -Have no articulation with the vertebral column. (Although the shoulder joints are not very stable, they are freely movable and thus allow movement in many directions.) *Each of the two Pectoral Girdles consist of two bones. 1) A clavicle ; and 2) A scapula 1. Clavicle or Collar Bones

-Are long, slender bones with a double curvature. -Are the anterior component and articulates with the sternum at the Sternoclavicular joint.

Sternal Extremity is the medial end of the clavicle where it articulates with the sternum.

Acromial Extremity is the lateral end of the clavicle where it articulates with the Acromion of the scapula, a joint called Acromioclavicular joint.

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2. Scapula or Shoulder Blades

-Are large, triangular, flat bone -Are the posterior component and articulate with clavicle and humerus. -Situated in the posterior part of the thorax between the levels of the second and seventh ribs.

Spine is a sharp ridge that runs diagonally across the posterior surface of the flattened, triangular body.

Acromion is the end of the spine that projects as a flattened expanded process; easily felt as the high point of the shoulder.

Glenoid Cavity (Fossa) a depression inferior to Acromion.

(This cavity articulates with the head of the humerus to form the shoulder joint.)

Medial (Vertebral) Border is the thin edge of the body near the vertebral column.

Lateral (Axillary) Border is the thick edge closer to the arm.

UPPER EXTREMITY Consist of 60 bones. *Each upper extremity includes: 1. Humerus- in the arm 2. Ulna and Radius - in the forearm 3. Carpals (wrist bones)

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4. Metacarpals (palm bones) 5. Phalanges in the fingers of the hand Humerus or Arm Bone

-Is the longest and largest bone of the upper extremity. -Articulates proximally with the scapula and distally at the elbow with both ulna and radius.

*Proximal end of the Humerus consists of:

Head - articulates with the glenoid cavity of the scapula.

Anatomical Neck - an oblique groove just distal to the head and the site of the epiphyseal plate.

Greater Tubercle - a lateral projection distal to the neck. It is the most palpable bony landmark of the shoulder region. Lesser Tubercle - an anterior projection.

*Between these tubercles runs an Intertubercular sulcus (bicipital groove).

Surgical Neck - a constricted portion just distal to the tubercles. Named because of its liability to fracture.

Body (shaft) cylindrical at the proximal end and gradually becomes triangular, flattened and broad at the distal end.

Deltoid Tuberosity a roughened, V-shaped area at the middle portion of the shaft. Serves as a point of attachment for the deltoid muscle.

*Distal end of the Humerus Consists of:

Capitulum a rounded knob that articulates with the head of the radius.

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Radial Fossa a depression that receives the head of the radius when the forearm is flexed.

Trochlea a pulleylike surface that articulates with the ulna.

Coronoid Fossa an anterior depression that receives part of the ulna when the forearm is flexed.

Olecranon Fossa a posterior depression that receives the Olecranon of the ulna when the forearm is extended.

Medial and Lateral Epicondyle are rough projections on either side of the distal end to which most muscles of the forearm are attached.

Ulna and Radius

Ulna is the medial bone of the forearm, located at the little finger side.

*Proximal end of the Ulna Consists of:

Olecranon (Olecranon Process) forms the prominence of the elbow.

Trochlear (semilunar) Notch a curved area between the olecranon and the coronoid process. The trochlea of the humerus fits into this notch.

Radial Notch a depression located laterally and inferiorly to the trochlear notch. It receives the head of the radius.

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*Distal end of Ulna Consists of:

Head separated from the wrist by a fibrocartilage disc.

Styloid Process on the posterior side of the distal end.

Radius is the lateral bone of the forearm, located on the thumb side.

*Proximal end of Radius Consists of:

Head is disc-shaped, and articulates with the Capitulum of the humerus and radial notch of the ulna.

Radial Tuberosity a roughened, raised area on the medial side. Is a point of attachment for the biceps brachii muscle. *Distal end of Radius Consists of:

Styloid Process on the lateral side.

Ulnar Notch on the medial side, but concave, for articulation with the distal end of the ulna.

Carpals, Metacarpals, and Phalanges

Carpus (or wrist) consists of eight small bones, the carpals, united to each other by ligaments.

4 Bones each in two transverse rows, named for their shapes: [Lateral to medial position in Anatomical position.]

Thumb (i) Scaphoid (resembles a boat) ⊥ (ii) Lunate (resembles a crescent moon in nits

anteroposterior aspect) (iii) Triquetrum (has three articular surfaces)

Small finger (iv) Pisiform (pea-shaped) - small finger, little finger

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Thumb (i) Trapezium (four-sided) ⊥ (ii) Trapezoid (four-sided)

(iii) Capitate (rounded projection, the head, articulate with the lunate)

Small finger (iv) Hamate (named for the large hook-shaped projection on anterior surface)

Metacarpus (meta=after) - with five bones that constitute the palm of the hand.

Each bone consist of a proximal base, medial shaft, and distal head.

The bones are number I to V, starting with the lateral bone (big short bone) in anatomical position.

*The heads of the metacarpals are commonly called the "knuckles", and are readily visible when the fist is clenched.

Phalanges with 14 bones that constitute the bones of the fingers.

Phalanx a single bone of the finger (or toe)

Each Phalanx consists of a: Proximal base, Medial shaft, and Distal head

First digit (thumb) has two phalanx called the Pollex (thumb).

Each of the remaining four digits; index finger, middle finger, ring finger, and little finger has three phalanx.

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PELVIC (HIP) GIRDLE

Pelvic (hip) Girdle consist of the two coxal bones or hipbones. (Provides a strong and stable support for the lower extremities on which the weight of the body is carried.) Pubic Symphysis where the two coxal bones (hip bones) unite. *Pelvis a basinlike structure formed by the unification of sacrum, coccyx, and the two coxal (hip) bones. *A newborn's Coxal (hip) bones consists three separate components: Ilium, Pubis, and Ischium. Acetabulum area of fusion for the three components (ilium, pubis, and ischium) as they eventually fuse into one. *Ilium is the largest of the three subdivisions of the coxal bone.

LOWER EXTREMITY

Are composed of 60 bones. 1. Femur in the thigh; 2. Patella (kneecap) 3. Fibula and Tibia in the leg; 4. Tarsals (ankle bone); 5. Metatarsals; and 6. Phalanges in the toes 1. Femur (thighbone) is the longest and heaviest bone in the

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body.

Head is the proximal end that articulates with acetabulum of the coxal bone.

Greater Trochanter and Lesser Trochanter are projections that serve as points of attachment for some of the thigh and buttock muscles.

Linea Aspera a rough vertical ridge on the posterior surface of diaphysis (shaft) of the femur.

Pathologic changes in the angle of the neck of the femur resulting in abnormal posture of the lower limbs:

a. "Knock-knee" condition - a decreased angle. b. "Bowleg" condition - abnormally large angle.

*Both conditions place an abnormal strain on the knee joints.

2. Patella

Patella (kneecap) is a small, triangular bone anterior to the knee joint.

Base the broad superior end.

Apex the pointed inferior end.

3. Tibia and Fibula

Tibia (shinbone) is the larger, medial bone of the leg.

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Lateral Condyle and Medial Condyle articulate with the condyles of the Femur.

Fibula is parallel and lateral with the fibula. Head on the proximal end articulates with the inferior surface of the lateral condyle of the tibia below the level of the knee joint.

Lateral Malleolus on the distal end articulates with the talus bone of the ankle.

*Pott's Fracture a fracture of the lower end of the fibula with injury to the tibia articulation.

4. Tarsals, Metatarsals, and Phalanges

Tarsus is a collective designation for the seven bones of the ankle called Tarsals.

Talus and Calcaneus are located on the posterior part of the foot.

Cuboid, Navicular, and three Cuneiform bones (first medial), second (intermediate), and third (lateral) cuneiform are located on the anterior part of the foot.

Talus (the uppermost) tarsal bone) is the only bone of the foot that articulates with the Fibula and tibia.

Metatarsus consists of five metatarsal bones numbered I to V from medial to later position.

*Like Metacarpals of the palm of the hand, each Metatarsal consist of a proximal Base, medial shaft, and a distal Head.

Phalanges of the foot resemble those of the hand both in number and arrangement.

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Each also consists of a proximal base, a middle shaft, and a distal head.

Hallus (greater or big toe) has two large, heavy phalanges called proximal and distal phalanges.

The other four toes each have three phalanges--proximal, middle, and distal.

Arches of the Foot Arches enable the foot to support the weight of the body, provide an ideal distribution of body weight over the hard and soft tissues of the foot, and provide leverage while walking. *Arches are not rigid; they yield as weight is applied and springs back when the weight is lifted, thus helping to absorb shocks.

a. Longitudinal Arch

b. Transverse Arch

FEMALE AND MALE SKELETONS -Generally bones of male are larger than those of female. -Articular ends of male's are thicker in relation to the shafts. -Points of attachment-tuberosities, lines, ridges-- are larger in the male skeleton since certain muscles of the male are larger than those of the female.

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