Ch.8 - The Skeletal System: The Appendicular Skeleton

Question 1

The appendicular skeleton includes:

Answer 1

the upper and lower extremities and the shoulder and hip girdles.

Question 2

The appendicular skeleton functions primarily to

Answer 2

facilitate movement

Question 3

Pectoral shoulder girdle

Answer 3

attaches the bones of the upper limbs to the axial skeleton. It includes the clavicle (collar bone) which lies horizontally in the superior and anterior part of the thorax superior to the first rib and articulates with the sternum and the clavicle(1) and the scapula (shoulder blade) articulates with the clavicle and the humerus (2). The glenoid cavity is the attachment point for the humerus and articulate with other bones anteriorly.

Clinical Connection:

Question 4

Upper Limb (Extremity)

Answer 4

Each upper limb consists of 30 bones including the:

1. Humerus - Longest and Largest bone of the upper limb; articulates proximally with the scapula and distally at the elbow with the radius and ulna.
2. Ulna - Located on the medial aspect of the forearm
3. Radius - Located on the lateral aspect of the forearm
   The radius and ulna articulate with the humerus, each other, and with three carpal bones.
4. Carpals (8) - bound together by ligaments that make up the wrist
5. Metacarpals - 5 metacarpal bones are contained in the palm of each hand
6. Phalanges - Each hand contains 14 phalanges; 3 in each finger and 2 in each thumb

Clinical Connection

Question 5

Pelvic (Hip) Girdle

Answer 5

The pelvic girdle consists of two hipbones (coal bones)and provides a strong and stable support for the lower extremities, on which the weight of the body is carried.

• Each hipbone is composed of three different bones at birth: (a) Illium - The larger of the three and articulates (fuses) with the ischium and pubis. (b) Pubis - The anterior and inferior part of the hipbone. (c) Ischium - The inferior and posterior portion of the hip bone; contains the Ischial Tuberosity (the part that meets the chair when you are sitting)
  They all eventually fuse at a depression called the acetabulum which forms the socket for the head of the femur.

Question 6

False and True Pelves

Answer 6

Together with the sacrum and coccyx, the two hipbones (coxal bones) form the pelvis.

The greater (false) pelvis is the bony pelvis superior to the pelvic brim

The lesser (true) pelvis is inferior to the pelvic brim

Clinical Connection

Question 7

Comparison of female and male pelves

Answer 7

• male bones are generally larger and heavier than female’s
• male joint surfaces tend to be larger
• Male muscle attachment is more well-defined due to larger muscle size
• Many anatomical differences between the pelvic girdles of females and males

Question 8

Lower Extremity

Answer 8

-Lower extremity is composed of 30 bones including the:

1. Femur - The largest, heaviest, strongest bone of the body
2. Patella - A sesamoid bone located anterior to the knee joint and forms the patellafemoral joint where it functions to increase the leverage of the tendon of the quadriceps femurs muscle, to maintain the position of the tendon when the knee is bent, and to protect the knee joint.
3. Tibia - The larger, medial, weight-bearing bone of the leg.
4. Fibula - parallel and lateral to the tibia and does NOT bear weight
5. Tarsals - 7 tarsal bones constitute the ankle and share weight associated with walking
6. Metatarsals - 5 metatarsal bones are contained in the foot
7. Phalanges - 14 bones in each foot; arrangement of the phalanges in the toes is the same as described for the fingers and thumb.

Arches in the foot - The bones are arranged in two nonrigid arches that enable the foot to support the weight of the body; provide an ideal distribution of body weight over the hard and soft tissues, and provide leverage while walking

Clinical Connection
Clinical Connection
Clinical Connection
Clinical Connection

Question 9

Development of the Skeletal System

Answer 9

Most skeletal tissue arises from mesenchymal cells, connective tissue cells derived from mesoderm.

• The bones that form directly within the mesenchyme from the through the process of intramembranous ossification
• Bones that form within hyaline cartilage are through the process of endochondral ossification

The Skull

• Begins development during the fourth week after fertilization
• Develops from mesenchyme around the developing brain and consists of two major portions: the neurocranium (mesodermal in origin) which forms the skull and viscerocranium (ectodermal in origin) which forms the bones of the face

Vertebrae and Ribs

• derived from portions of cube-shaped masses of mesoderm called somites
• mesenchymal cells from these regions surround the notochord at about 4 weeks after fertilization
• The notochord is a solid cylinder of mesodermal cells

The Skeletal of the Limbs

• Derived from mesoderm
• The upper limbs appear as small elevations at the sides of the trunk called upper limb buds
• The limb buds consist of mesenchyme covered by ectoderm
• By the sixth week, the limb buds develop a constriction around the middle portion
• By the seventh week, the arm, forearm, and hand are evident in the upper limb bud, and the thigh, leg, and foot appear in the lower limb bud
• By the eighth week, the shoulder, elbow, and wrist areas become apparent
• By the twelfth week, primary ossification centers are present in most of the limbs
• Most secondary ossification centers appear after birth

Question 10

Disorders: Homeostatic Imbalances

Answer 10

The term “hip fracture” most commonly applies to a break in the bones associated with the hip joint. They often require surgical treatment.

Question 11

Medical Terminology

Answer 11

1. Clubfoot or talipes equinovarus
2. Genu Valium
3. Genu Varum
4. Hallux Valgus