Bony Thorax

Characteristics

1. Support the shoulder girdle and upper limbs

2. Protect the viscera in the thoracic and upper abdominal cavities

3. Play a role in breathing

Sternum

3 fused bones

1. Manubrium

2. Body

3. Xiphoid process

Ribs

12 pair of ribs that attach posteriorly to the Thoracic Vertebrae and then curve downward and forward toward the anterior body surface.

The ribs increase in length from 1 to 7 and then decrease in length from 8 to 12.

RibsTrue Ribs: upper 7 that are attached to the

sternum by costal cartilage

False Ribs: remaining 5; either attach indirectly to the sternum or lack sternal attachment entirely

Floating Ribs: pairs 11 & 12; have no anterior attachment; their costal cartilages lie embedded in the muscles of the lateral body wall

Ribs

Appendicular Skeleton

Pectoral (Shoulder) Girdle(open girdle)

Supports the upper limbs

Attachment for several muscles that move the upper limbs

Clavicle (Collarbone)

Braces the freely movable scapulae, helping to hold the shoulder in place.

Provides attachment for muscles of the upper limbs, chest, and back.

Scapulae (Shoulder Blades)

Triangular bones located on either side of the upper back.

A spine divides the posterior surface of each scapula into unequal portions.

Scapulae (Shoulder Blades)

The spine leads to 2 processes:

1. Acromium process that forms the tip of the shoulder; articulates with the clavicle

2. Coracoid process that curves anteriorly and inferiorly to the clavicle

Scapulae (Shoulder Blades)

Scapulae (Shoulder Blades)

Scapulae (Shoulder Blades)

Between the process is a depression called the glenoid cavity that articulates with the head of the humerus (arm bone)

The Upper Limbs

Humerus:

Forearm

Ulna:

Radius:

Hand

Carpus: 8 bones in 2 rows

Hand

Metacarpals: Palm, 1 to 5 from thumb to little finger

Phalanges:

Fingers, 14 bones

The Pelvic (Hip) Girdle(closed girdle)

1. Attaches the lower limbs to the axial skeleton

2. Supports the visceral organs of the pelvic cavity

3. Formed by the 2 coxal bones that articulate anteriorly at the symphysis pubis and posteriorly with the sacrum

4. The 3 bones fuse in the region of a cup-shaped cavity called the acetabulum, which receives the rounded head of the femur

Coxal Bones

3 fused bones:1. Ilium – Largest and uppermost portion that forms the prominance of the hip (iliac crest); joins the sacrum to form the sacroiliac joint

2. Ischium – lowest portion; L-shaped; ischial tuberosity points posteriorly and downward and supports the weight of the body when sitting; ischial spine near the junction of the ilium and ischium

3. Pubis – anterior portion forms the joint called the symphysis pubis; joins with the ischium to form the largest foramen in the skeleton, the obturator foramen

Coxal Bones

Iliac Crest

Ilium

Ischium Pubis

acetabulum

Obturator foramen Ischial

tuberosity

Ischial Spine

Pelvic Structure and Childbearing

1. False Pelvis: portion superior to the pelvic brim2. True Pelvis: region inferior to the pelvic brim that is

almost entirely surrounded by bone and forms a deep “bowl” containing the pelvic organs

3. Pelvic Inlet: pelvic brim; widest dimension is along the frontal plane

4. Pelvic Outlet: inferior margin of the true pelvis; bounded anteriorly by the pubic arch, laterally by the ischia, and posteriorly by the sacrum; since both the coccyx and the ischial spines protrude into the outlet, a sharply angled coccyx or large spines can cause problems during childbirth

Comparison of the Male & Female Pelvis

Male FemaleCharacteristic Female Male

General Structure & Functional Modifications

Tilted forward, modified for childbearing; cavity of the true pelvis is broad, shallow, and has a greater capacity

Tilted backward; adapted for support of a strong body; cavity of the true pelvis is narrow and deep

Bone Thickness Less; bones lighter, thinner and smoother

Greater; bones heavier and thicker, and markings are more prominent

Acetabulum Smaller; farther apart Larger; closer together

Pubic angle/arch Broader (over 90o), more rounded

Angle is more acute (less than 90o)

The Lower Limbs

1. Carry the entire weight of the erect body

2. Subjected to exceptional forces when jumping and running

3. Thicker and stronger than comparable bones of the upper limbs

Femur (thigh)Longest bone in the body

Tibia (shin)

Located on the medial side

Fibula

Non weight bearing bone

Located laterally

Patella

Knee Cap

Tarsus/Metatarsus/Phalanges

Foot

Arches of the Foot

“A segmented structure can only hold up weight if it is arched.”

The foot has 3 arches that “give when weight is applied to the foot and spring back when the weight is removed:2 longitudinal

1. Medial 2. Lateral

1 transverse

Arches of the Foot

Arches of the Foot