Chapter 6 Questions

Three organic components of the bone matrix.

1) Collagen 2) Various large protein-carbohydrate complexes called glycosaminoglycans, proteoglycans, and glycoproteins.

Fractures are the most common bone disorder.

False

What does hemopoietic tissue mean?

Blood-forming tissue

The five tissues found in bone

1) Blood 2) Cartilage 3) Adipose Tissue 4) Nervous Tissue 5) Fibrous Connective Tissue

The principal hormones that stimulate bone growth.

1) Calcitonin: Hormone secreted by the thyroid gland, stimulates osteoblast activity. Functions chiefly in children and pregnant women. 2) Growth Hormone: Promotes intestinal absorption of calcium, the proliferation of cartilage at the epiphyseal plates, and the elongation of bones. 3) Sex Steroids: Stimulate osteoblasts and promote the growth of long bones, especially in adolescence.

The nutrients most important to bone growth.

1) Calcium and phosphate are needed as raw materials for the calcified ground substance of bone. 2) Vitamin A promotes synthesis of the glycosaminoglycans of the bone matrix. 3) Vitamin C promotes the cross-linking of collagen molecules in bone and other connective tissues. 4) Vitamin D is necessary for calcium absorption by the small intestine, and it reduces the urinary loss of calcium and phosphate.

Name and describe 5 types of bone fractures.

1) Closed: Skin is not broken 2) Complete: Bone is broken into two or more pieces 3) Nondisplaced: The portions of bone are still in correct anatomical alignment 4) Impacted: One bone fragment is driven into the marrow cavity or spongy bone of the other 5) Spiral: Fracture spirals around axis of long bone as the result of a twisting stress such as as a skiing accident

Compact vs. Spongy Bone

1) Compact Bone: Outer shell of the bone composed of dense white osseous tissue - Encloses the medullary (marrow cavity) in the middle of the bone. 2) Spongy Bone: The ends of the bone that is a more loosely organized form of osseous tissue.

Calcitriol is made from ____.

7-dehydrocholesterol

A bone increases in diameter only by ____ growth, the addition of new surface lamellae.

Appositional

The ends of the bone are covered with a layer of hyaline cartilage called the ____.

Articular Cartilage

Osteocytes contact each other though channels called ____ in the bone matrix.

Canaliculi

One long bone meets another at its ____.

Epiphysis

Osteoclasts develop from osteoblasts.

False

The growth zone of the long bones of adolescents is the articular cartilage.

False

The protein of the bone matrix is called hydroxyapatite.

False

Yellow bone marrow has a hemopoietic function.

False

Calcium phosphate crystallizes in bone as a mineral called ____.

Hydroxyapatite

What are the mineral crystals of bone called and what are they made of?

Hydroxyapatite: A crystallized calcium phosphate salt = 10% calcium carbonate; and lesser amounts of magnesium, sodium, potassium, fluoride, sulfate, carbonate, and hydroxide ions. The minerals resist compression (crumbling or sagging when weight is applied).

The medullary cavity of a child's bone may contain ____.

Red Bone Marrow

Which type of bone marrow fits the description of 'hemopoietic tissue?

Red Bone Marrow

Major risk factors for osteoporosis and ways to prevent it.

Risk Factors: Bone density declines to the extent that the bones become brittle and subject to pathological fractures - Involves the loss of proportionate amounts of organic matrix and minerals, especially from the spongy bone. The bone becomes insufficient in quantity to support the body's weight and withstand normal stresses. Bones are especially subject to fractures which can lead to immobility. Spinal deformity is also common. Prevention: Weight bearing exercise and ample calcium and protein intake early in life.

The transitional region between epiphyseal cartilage and the primary marrow cavity of a young bone is called the ____.

Metaphysis

Osteoclasts are most closely related by common descent to ____.

Monocytes

The cells that deposit new bone matrix are called ____.

Osteoblasts

Which cells have a ruffled border and secrete hydrochloric acid?

Osteoclasts

Most compact bone is organized in cylindrical units called ____, composed of lamellae encircling a central canal.

Osteons

The most common bone disease is ____.

Osteoporosis

How does Wolff's law explain some of the structural differences between the bones of a young child and the bones of a young adult?

States that the architecture of a bone is determined by the mechanical stresses placed upon it, and the bone thereby adapts to withstand those stresses. Shows that the form of a bone is shaped by its functional experience.

The ____ glands secrete a hormone that stimulates cells to resorb bone and return its minerals to the blood.

Parathyroid

Why do X-rays of a child's limbs exhibit a clear line between the epiphysis and diaphysis of a long bone?

The epiphyseal plate of hyaline cartilage separates the marrow cavities of the epiphysis and diaphysis. This is the zone where the bones grow in length.

Blood vessels travel through the central canals of compact bone.

True

Most bones develop from hyaline cartilage.

True

Osteocytes develop from osteoblasts.

True

Parathyroid hormone promotes bone resorption and raises blood calcium concentration.

True

True/False Spongy bone is normally covered by compact bone.

True

Compact and Spongy bone in long bones vs. flat bones

1) Long Bone: Compact bone covers the whole outer shell of the bone, specifically in the middle diaphysis where the marrow cavity is. Then the spongy bone is located in the two ends of the long bone still covered by the compact bone. 2) Flat Bone: Have a sandwich like construction, with two layers of compact bone enclosing a middle layer of spongy bone.

Stages of intramembranous ossification.

1) Mesenchyme first condenses into a soft sheet of tissue permeated with blood vessels - Mesenchymal cells line up along the blood vessels, become osteoblasts, and secrete a soft collagenous osteoid tissue in the direction away from the vessel. 2) Calcium phosphate and other minerals crystallize on the collagen fibers of the osteoid tissue and harden the matrix. Continued osteoid deposition and mineralizations squeeze the blood vessels and future bone marrow into narrower spaces. As osteoblasts become trapped in their own hardening matrix, they become osteocytes. 3) More of the mesenchyme adjacent to the developing bone condenses and forms a fibrous periosteum on each surface. Spongy bone becomes a honeycomb of slender calcified trabeculae. 4) At the surfaces, osteoblasts beneath the periosteum deposit layers of bone, fill in the spaces between trabeculae, and create a zone of compact bone on each side, as well as thickening the bone overall. Gives rise to the flat bone sandwich like structure.

Four kinds of bone cells and their neighboring tissues.

1) Osteogenic Cells: Stem cells found in the endosteum, the inner layer of the periosteum, and within the central canals. Arise from embryonic mesenchyme. They multiply continually and give rise to the osteoblasts. 2) Osteoblasts: Bone forming cells that synthesize the organic matter of the matrix and help to mineralize the bone. They line up in rows in the endosteum and inner layer of periosteum and resemble a cuboidal epithelium on the bone surface. 3) Osteocytes: Former osteoblasts that have become trapped in the matrix they deposited. Live in the lacunae and communicate through the gap junctions to the osteoblasts on the bone surface. Some resorb bone matrix and others deposit it so they contribute to the homeostatic maintenance of both bone density and blood concentration of calcium and phosphate. 4) Osteoclasts: Bone dissolving macrophages found on bone surfaces Develop from the same bone marrow stem cells that give rise to blood cells. The very acidic pH dissolves the minerals of the adjacent bone.

What are the two kinds of bone marrow?

1) Red Bone Marrow: Gets its color from an abundance of red blood cells. Called 'myeloid tissue' but is best regarded as an organ. Also described as 'hemopoietic', or blood forming tissue b/c all types of blood cells are produced here. 2) Yellow Bone Marrow: Fatty - No longer produces blood, although in the event of severe or chronic anemia it can transform back into res marrow and resume that role.

Anatomical terms for the shaft, head, growth zone, and fibrous covering of a long bone.

1) Shaft: Diaphysis 2) Head: Epiphysis 3) Growth Zone: Epiphyseal Plate 4) Fibrous Covering of a Long Bone: Periosteum

What is a callus? How does it contribute to fracture repair?

1) Soft Callus: Deposition of collagen and fibrocartilage converts granulation tissue to a soft callus. 2) Hard Callus: Osteoblasts deposit a temporary bony collar around the fracture to unite the broken pieces while ossification occurs.

7 Functions of the Skeletal System

1) Support: Bones provide support for muscles. 2) Movement: Ability to move the bones. 3) Protection: Bones enclose delicate organs and tissues. 4) Blood Formation: Red bone marrow is the major producer of blood cells, including most cells of the immune system. 5) Electrolyte Balance: Main reservoir of calcium and phosphate - stores them and releases them when needed. 6) Acid Base Balance: Bone buffers the blood against excessive pH changes by absorbing or releasing alkaline salts such as calcium phosphate. 7) Detoxification: Bone tissue absorbs heavy metals and other foreign elements from the blood the thus mitigates their toxic effects on other tissues.

5 zones of a metaphysis and the major distinctions between them.

1) Zone of Reserve Cartilage: Farthest from the marrow cavity, consists of typical resting hyaline cartilage. 2) Zone of Cell Proliferation: A little closer to the marrow cavity, chondrocytes multiply and arrange themselves into longitudinal columns of flattened lacunae. 3) Zone of Cell Hypertrophy: The chondrocytes cease to multiply and begin to hypertrophy (enlarge). The walls of the matrix between lacunae become very thin. 4) Zone of Calcification: Minerals are deposited in the matrix between the columns of lacunae and calcify the cartilage. These are only temporary support for the cartilage that would otherwise soon be weakened by the breakdown of the enlarged lacunae. 5) Zone of Bone Deposition: Within each column, the walls between the lacunae break down and the chondrocytes die. This converts each column into a longitudinal channel, which is immediately invaded by blood vessels and marrow from the marrow cavity. Osteoblasts line up along the walls of these channels and begin depositing concentric lamellae of the matrix, while osteoclasts dissolves the temporarily calcified cartilage.

Which of these does not promote bone deposition? A) Dietary Calcium B) Vitamin D C) Parathyroid Hormone D) Calcitonin E) Testosterone

C) Parathyroid Hormone

A child jumps to the ground from the top of a playground. His leg bones do not shatter mainly because they contain ____.

Collagen Fibers

The cranial bones develop from a flat sheet of condensed mesenchyme in a process called ____.

Intramembranous Ossification

One sign of osteoporosis is ____.

Kyphosis

The walls between cartilage lacunae break down in the zone of ____.

Reserve cartilage

The long bones of the limbs grow in length be cell proliferation and hypertrophy in ____.

The metaphysis