Describe the structural components of
The basic functional unit of compact bone is the osteon (or Haversian system), which has a central canal and concentric layers of osteocytes in lacunae known as lamellae. Perforating canals link the blood vessels of central canals with those of the periosteum and marrow cavity.
Giant cells that have 50 or more nuclei and secrete osteolytic enzymes are called which of the following?
How does spongy bone differ structurally from compact bone?
Spongy bone differs from compact bone in that it has a different lamellar arrangement and contains no osteons. Instead, the lamellae form rods or plates called trabeculae, whose frequent branchings create an open network. Canaliculi radiating from the lacunae of spongy bone end at the exposed surfaces of the trabeculae, where nutrients and wastes diffuse between the marrow and osteocytes.
Discuss the importance of vitamin D3 in normal calcium metabolism.
Vitamin D3 can be obtained from dietary supplements or manufactured by epidermal cells exposed to UV radiation. After it has been processed in the liver, the kidneys convert a derivative of this vitamin into calcitriol, a hormone that stimulates the absorption of calcium and phosphate ions in the digestive tract.
Define and describe the process of intramembranous ossification
Intramembranous ossification is the process by which bone develops within sheets or membranes of connective tissue. This process begins when osteoblasts differentiate within embryonic or fetal fibrous connective tissue. This type of ossification normally occurs in the deeper layers of the dermis. The osteoblasts differentiate from connective tissue stem cells after the organic components of the matrix (secreted by the stem cells) become calcified.
Cartilage forming cells from perichondrium secrete new matrix against the external face of existing cartilage;Growth from the outside
Why is regular exercise important in
maintaining normal bone structure?
As a result of regular exercise, heavily stressed bones become thicker and stronger and develop more pronounced surface ridges. In contrast, bones not subjected to ordinary stresses become thin and brittle.
What roles do the hormones, parathyroid hormond (PTH), calcitonin, and clacitriol, play in maintaining calcium homeostasis?
TH (from the parathyroid glands) and calcitriol (from the kidneys) work together to elevate calcium levels in body fluids. Their actions are opposed by calcitonin, a thyroid gland hormone that depresses calcium levels in body fluids.
In adults, osteocytes in lacunae maintain the matrix, removing and replacing the surrounding ...
Bones can heal after severe damage, as long as the __________ remains and the cellular components of the periosteum and endosteum survive.
inadequate ossification is termed ...
How do osteoporosis and osteopenia differ?
Osteoporosis is a condition that produces a reduction in bone mass great enough to compromise normal function. The difference between the "normal" osteopenia (inadequate ossification) of aging and the clinical condition of osteoporosis is a matter of degree
Describe the appendicular skeleton, including its location and number of bones.
The appendicular skeleton includes the bones of the limbs and those of the pectoral and pelvic girdles, which attach the limbs to the trunk. Altogether, there are 126 appendicular bones; 32 are associated with each upper limb, and 31 with each lower limb.
An extension of bone making an angle with the rest of the structure is called a ...
Describe the axial skeleton, including its location and number of bones.
The axial skeleton forms the longitudinal axis of the body. There are 80 bones in this division, which can be subdivided into (a) the 22 bones of the skull, plus 7 associated bones (6 auditory ossicles and the hyoid bone); (b) the thoracic cage (rib cage), which is composed of 24 ribs and the sternum; and (c) the 26 bones of the vertebral column.
The pectoral girdle consists of two pairs of bones: the __________.
scapulae and clavicles
How does the pelvis in females differ from the pelvis in males?
The shape of the pelvis in females is somewhat different from that in males. Some of the differences result from variations in body size and muscle mass. In females, the pelvis is generally smoother, lighter in weight, and has less-prominent markings.
Other differences are adaptations that aid in supporting the weight of the developing fetus and easing passage of the newborn through the pelvic outlet during delivery. (The pelvic outlet is the inferior opening of the pelvis bounded by the coccyx, the ischia, and the pubic symphysis.)
Compared to males, females have a relatively broad, low pelvis, a larger pelvic outlet, and a broader pubic angle (the angle between the pubic bones).