Chapter 6, 7 , and 8 Study Guide for AP

What does the skeletal system include?

Bones, joints, and associated supporting tissues.

What tissues are found in bones besides osseous tissue?

Dense regular and irregular collagenous connective tissue, and bone marrow.

What bones protect underlying organs?

Skull, sternum, ribs, and pelvis.

What minerals are stored in bone?

Calcium, phosphorus, and magnesium salts.

What is the role of bone in acid–base homeostasis?

It stores minerals that act as electrolytes, acids, and bases.

What is hematopoiesis?

The formation of blood cells in red bone marrow.

What is yellow bone marrow made of?

Fat cells (adipocytes) that store triglycerides.

How do bones contribute to movement?

Muscles attach to bones and pull on them to generate movement at joints.

How do bones provide support?

They support body weight and form the structural framework.

What are the five bone shape categories?

Long, short, flat, irregular, and sesamoid.

What defines a long bone?

Longer than wide; includes most bones in arms and legs.

What defines a short bone?

Cube-shaped; includes carpals and tarsals.

What defines a flat bone?

Thin and broad; includes ribs, pelvis, sternum, and skull bones.

What defines an irregular bone?

Irregularly shaped; includes vertebrae and certain skull bones.

What defines a sesamoid bone?

Small, flat, oval-shaped bones within tendons; e.g., patella.

What is the periosteum?

Dense irregular connective tissue membrane covering outer surface of long bones.

What are perforating (Sharpey’s) fibers?

Collagen fibers anchoring periosteum to bone matrix.

What is the diaphysis?

Shaft of a long bone.

What is the epiphysis?

The end of a long bone.

What is articular cartilage?

Hyaline cartilage covering epiphyses at joints.

What is the medullary cavity?

Marrow-filled cavity within the diaphysis.

What is compact bone?

Dense outer bone that resists compression and twisting.

What is spongy bone?

Honeycomb-like inner bone that resists multidirectional forces.

What is the endosteum?

Thin membrane lining inner surfaces of bone and covering spongy bone struts.

What are epiphyseal lines?

Remnants of growth plates separating epiphyses from diaphysis.

What bones lack diaphyses and epiphyses?

Short, flat, irregular, and sesamoid bones.

What is diploë?

Spongy bone layer between compact bone layers in flat bones.

What are sinuses in bones?

Air-filled spaces that reduce bone weight.

How do short, flat, irregular, and sesamoid bones receive blood?

From vessels in the periosteum.

How do long bones receive blood?

One-third from periosteum; two-thirds from nutrient arteries.

What is the nutrient foramen?

Small hole in diaphysis where nutrient arteries enter.

Where is red bone marrow found in adults?

Pelvis, proximal femur and humerus, vertebrae, ribs, sternum, clavicles, scapulae, and some skull bones.

What is yellow bone marrow composed of?

Triglycerides, blood vessels, and adipocytes.

What is bone marrow transplantation used to treat?

Leukemia, sickle-cell anemia, and aplastic anemia.

What is the inorganic matrix of bone made of?

Calcium and phosphorus salts forming hydroxyapatite crystals.

What is the organic matrix of bone called?

Osteoid.

What proteins are found in osteoid?

Collagen, proteoglycans, glycosaminoglycans, glycoproteins.

What does collagen do in bone?

Resists torsion and tensile forces.

What do proteoglycans and glycosaminoglycans do?

Create osmotic gradient to resist compression.

What do glycoproteins do in bone?

Bind components of osteoid and inorganic matrix.

What are osteoblasts?

Bone-building cells that perform bone deposition.

What are osteogenic cells?

Precursor cells that differentiate into osteoblasts.

What is bone deposition?

Secretion of organic matrix and formation of inorganic matrix by osteoblasts.

What are osteocytes?

Mature bone cells that maintain bone matrix.

Where are osteocytes located?

In lacunae.

What can osteocytes do under tension?

Recruit osteoblasts to reinforce bone.

What are osteoclasts?

Multinucleated cells that perform bone resorption.

How do osteoclasts break down bone?

Secrete hydrogen ions and enzymes.

What happens to substances released by osteoclasts?

Absorbed into cytosol and released into blood.

What is an osteon?

Structural unit of compact bone.

What are lamellae?

Concentric rings of bone matrix in osteons.

What is the central canal?

Endosteum-lined hole in center of osteon containing blood vessels and nerves.

What are canaliculi?

Small passageways connecting lacunae for cell communication.

What are interstitial lamellae?

Remnants of old osteons between current osteons.

What are circumferential lamellae?

Lamellae lining the outer and inner surfaces of compact bone.

What are perforating (Volkmann’s) canals?

Canals connecting central canals of osteons.

What are trabeculae?

Struts of spongy bone covered with endosteum.

How does spongy bone receive blood?

From vessels in bone marrow.

What is osteopetrosis?

A disease caused by defective osteoclasts leading to brittle bones.

What is ossification?

The process of bone formation.

What is primary bone?

Immature bone with irregular collagen and sparse inorganic matrix.

What is secondary bone?

Mature bone with more inorganic matrix and strength.

What is intramembranous ossification?

Bone formation from mesenchymal membrane; forms flat bones.

What is endochondral ossification?

Bone formation from hyaline cartilage; forms most bones.

What is a fontanel?

Soft spot in a newborn’s skull due to incomplete ossification.

What is the bone collar?

Early bone formed around cartilage model in endochondral ossification.

What is the medullary cavity?

Central cavity in long bones formed during ossification.

What remains after ossification is complete?

Articular cartilage and epiphyseal plates.

What is osteoporosis?

Bone disease with weak, brittle bones due to low inorganic matrix.

What causes osteoporosis?

Calcium/vitamin D deficiency, age, estrogen loss, inactivity, genetics.

How is osteoporosis diagnosed?

Bone density measurement.

What prevents osteoporosis?

Balanced diet, exercise, and hormone therapy.

What is longitudinal growth?

Bone lengthening at epiphyseal plate via chondrocyte division.

What are the five zones of the epiphyseal plate?

Reserve cartilage, proliferation, hypertrophy, calcification, ossification.

What happens in the zone of proliferation?

Chondrocytes divide actively.

What happens in the zone of hypertrophy?

Chondrocytes enlarge and stop dividing.

What happens in the zone of calcification?

Chondrocytes die and matrix calcifies.

What happens in the zone of ossification?

Osteoblasts lay down bone on calcified cartilage.

When does longitudinal growth stop?

Between ages 18–21 when epiphyseal plate closes.

What is appositional growth?

Bone growth in width via osteoblasts under periosteum.

What is achondroplasia?

Genetic disorder causing dwarfism due to abnormal cartilage growth.

What hormone stimulates bone growth?

Growth hormone.

What does testosterone do to bone?

Increases thickness and growth rate; accelerates epiphyseal plate closure.

What does estrogen do to bone?

Increases growth rate and inhibits osteoclasts; closes epiphyseal plate faster.

What is gigantism?

Excess growth hormone in childhood causing tall stature.

What is acromegaly?

Excess growth hormone in adulthood causing bone and tissue enlargement.

What is bone remodeling?

Continuous process of bone deposition and resorption.

What is the function of osteoblasts in remodeling?

To build new bone matrix during deposition.

What is the function of osteoclasts in remodeling?

To break down bone matrix during resorption.

What is the role of the endocrine system in bone growth?

Hormones regulate cell division, matrix production, and epiphyseal plate activity.

What gland secretes growth hormone?

The anterior pituitary gland.

What does growth hormone stimulate in bone?

Chondrocyte division, osteogenic cell activity, and osteoblast function.

What does testosterone do to bone?

Increases appositional growth, mitosis in epiphyseal plate, and accelerates plate closure.

What does estrogen do to bone?

Increases longitudinal growth, inhibits osteoclasts, and accelerates epiphyseal plate closure.

Why do females tend to be shorter than males?

Estrogen closes the epiphyseal plate faster than testosterone.

What causes gigantism?

Excess growth hormone before epiphyseal plate closure.

What causes acromegaly?

Excess growth hormone after epiphyseal plate closure.

What are symptoms of acromegaly?

Enlargement of bones, cartilage, and soft tissues—especially in the face, hands, and feet.

What is the zone of reserve cartilage?

Region of epiphyseal plate with inactive chondrocytes that can be recruited for growth.

What is the zone of proliferation?

Region with actively dividing chondrocytes in lacunae.