Chapter 5

What is the difference between compact and spongy bone?

--They have different arrangements of bone cells --compact have a dense outer layer with few spaces, are covered with the periostem. Has yellow fat marrow. Located in shaft of long bones. --spongy bones have a latticework of bone. Red blood marrow. Located in small flat bones in skull, head, near ends of shaft (long) bones.

Explain how a bone heals after it has been fractured.

1. A blood clot is formed at the site of the fracture. 2. Fibroblasts secrete collagen fibers, which form a fibrocartilaginous callus that is replaced by a bony callus. 3. Over time, bone remodeling restores the bone to the original shape

Describe the formation of bone in a fetus. Explain how bone growth continues after birth.

1. During fetal development, most of the skeleton is first formed of cartilage. Cartilage cells actively divide, allowing the skeleton to grow as the fetus does. 2. Beginning around the third month of development, osteoblasts (bone-forming cells) form a ring of bone around the cartilage cells to degenerate, forming the center cavity of the bone. Osteoblasts then fill the cavity with spongy bone. 3. After birth, bones grow longer as the cartilage cells in the growth plates at the ends of the bone divide. Bone replaces the newly formed cartilage. 4. At puberty, hormones usually cause an increase in the rate of growth that lasts until the end of teenage years (usually about age 18), when cartilage cells slow their rate of division.

Describe a synovial joint.

A synovial joint is a freely movable joint, such as the knee joint. A think layer of cartilage reduces the friction on the surfaces of the ones that slide over one another. A synovial joint is surrounded by a two-layered joint capsule. The synovial membrane, which forms the inner layer of the capsule, secretes synovial fluid to lubricate the joint. Ligaments hold the joint together, support the joint, and determine the direction of movement at the joint.

What is bone remodeling? Explain the role of osteoblasts and osteoclasts. How does stress on the bones affect remodeling?

Bone remodeling is the continuous reshaping and replacing of bone during one's lifetime. Osteoblasts continuously form bone while osteoclasts continuously break down bone. Bone is built along the lines fo stress on a bone, providing strength where it is needed the most.

The cells that form bone are called ____________.

Osteoblasts

What functions do bones perform?

S-Support M-Movement P-Protects internal organs M-storage of Minerals (phosphorus and calcium) F-Storage of fat B-Blood cell production (Some Men Pee Melons while playing Foot Ball)

Describe the axial and appendicular parts of the skeleton.

The axial skeleton includes the bones of the skull, vertebral column, rib cage, and sternum. The appendicular skeleton includes the bones of the pectoral girdle and arms, and the bones of the pelvic girdle and legs.

Describe the structure of an osteon, and explain the function of osteocytes and the central canal.

The osteon consists of a central canal surrounded by concentric rings of osteocytes (mature bone cells) in a rigid matrix. Osteocytes are located within a lacuna in the matrix. Canals connect the lacunae to each other and to the central canal. This allows for the transport of items between the cells and the blood vessels in the central canal.

Of the following persons, which one would you expect to have the densest bones? a. an elderly women who knits b. a 16-year-old girl who swims regularly c. 33 year old male who likes milk and playing basketball d. 50 year old workaholic with a desk job

c. 33 year old male who likes milk and playing basketball

Which of the following is not a bone of the axial skeleton? a. skull b. vertebra c. femur d. sternum

c. femur

Bone hardens by the minerals __________ and _________.

calcium and phosphorus

Which bones comprise the pectoral girdle?

clavicle and scapula

___________ hold(s) two bones together at a joint.

ligaments

The action opposite to extension is

flexion

The ______________ is a movable bone in the skull.

mandible

The functional units of compact bone are called

osteons

______________ is a decrease in bone density that causes a weakened bone.

osteoporosis

Which hormones raises the blood level of calcium?

parathyroid hormone

A ______________ is the overstretching or tear in a ligament that may cause pain after the injury.

sprain

Where in a bone is fat stored?

yellow bone marrow (within compact bone)