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Chapter 7– Bone Tissue

Ch. 7 Study Guide 1. Critically read Chapter 7:

A. 7.1-7.2 (pp. 206-214) right before section 7.3 (Bone Development)

B. 7.4 (Physiology of Osseous Tissue) section (pp. 220-224) before section 7.5 (Bone Disorders)

C. Deeper Insight boxes 7.1, 7.2, & 7.4 (Osteoporosis)

2. Comprehend Terminology (those in bold in the textbook) within the reading scope above

3. Study-- Figure questions, Think About It questions, and Before You Go On (section-ending) questions (within the reading scope above)

4. Do end-of-chapter questions—s– Testing Your Recall— 1, 3-4, 6-12, 15-20– True or False– 1, 2, 4-10

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§ Quotable Quotes

The University of Nebraska says that elderly people that drink beer or wine at least four times a week have the highest bone density.

They need it - they're the ones falling down the most. – Jay Leno

I-- 7.1. Introduction

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§ Bone and Skeleton• The study of bone– Osteology

– Osseous—pertaining to bone– Osteon— structural unit of . . .– Osteocyte—a mature bone cell– Osteoporosis—a degenerative bone disease;

loss of bone mass due to . . .

• Functions of the skeletal system– support, protection, movement, electrolyte

balances, acid-base balance and blood formation

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§ Bone (Osseous tissue)— A connective tissue or an organ?

• A connective tissue (C.T.; osseous tissue) with a matrix hardened by minerals (mainly calcium phosphate)– a process called ___________________.

• “Bone”—denotes as an organ; individual bones consist of many tissues--osseous tissue, marrow, blood, cartilage, nervous tissue

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§ Shapes of Bones-- 4 groups• 1. Long bones –longer

than wide; levers acted upon by muscles; Ex. humerus

• 2. Short bones – nearly equal in length and width; Ex. carpal and tarsal bones

• 3. Flat bones – protect soft organs and provide for muscle attachment; Ex. scapula

• 4. Irregular bones —the vertebrae and some skull bones

§ Structures of long bones (A)--

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1. Diaphysis —its shaft; function:

2. Epiphysis — heads at each end; functions:

3. Articular cartilage – The joint surface where one bone meets another is covered with a layer of hyaline cartilage

Fig. 7.2

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2

3

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1. Epiphyseal plate (growth plate; in children)— What is it?

2. Epiphyseal line (in adults)—

Fig. X and Y

§ Structures of long bones (B)--

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In children

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An adult bone

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§ Flat Bone of the Cranium1. Sandwich like arrangement--

2. Middle layer is _________________

A.Trabeculae-- A lattice of slender rods and spines;

3. Skull fracture may fracture the outer layer of compact bone, but leave inner layer of compact bone unharmed

Fig. 7.3

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Match the following bones to these four bone shapes

1. _____ Vertebrae, sphenoid, ethmoid

2. _____ The three bones in each of your fingers and toes (phalanges), humerus

3. _____ Ribs, scapula, most skull bones, sternum

4. _____ Kneecap (patella), calcaneus

A. Long bone B. Short bone

C. Flat bone D. Irregular bone

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II-- 7.2. Histology of Osseous Tissue

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§ 1--Four Types of Bone Cells (1)1. Osteogenic cell 2. Osteoblast 3. Osteocyte

1. Osteogenic cells (Stem cells) in endosteum, periosteum or central canals give rise to new osteoblasts

2. Osteoblasts (called ____________) form bone matrix

3. Osteocytes are former osteoblasts trapped in the matrix they formed; shape? Functions? (a) maintain bone density; (b) blood conc. of . . . (c) strain sensors

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§ 1--Four Types of Bone Cells (2)

4. Osteoclasts (bone-dissolving cells) develop in bone marrow by fusion of 3-50 stem cells; appearance? Location:A. Reside in pits (called resorption bays)

that they ate into the bone

B. Bone remodeling– combined action of . . .

Fig. 7.4b

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Check point question

1. Mature bone cells are known as _______.

2. Bone-building cells are called ________,

3. __________ are bone-resorbing cells.

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§ 2--Matrix of Osseous Tissue• Dry weight = 2/3 inorganic; 1/3 organic matter1. Inorganic matter—supports the weight

– 85% hydroxyapatite– this is calcium phosphate salt

– 10% calcium carbonate; 5% other minerals– Disease —Rickets; bone softening and

deformity (Fig. x) or osteomalacia in adults2. Organic matter—gives flexibility

– Collagen; Protein-CHO complexes– Disease – Brittle bone disease; a defect in

collagen deposition (Fig. x)

3. Combination 1 and 2 above provides for strength and resilience

4. Read Deeper Insight 7.1 (Bone Contamination)

Rickets

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Also called-- Osteogenesis imperfecta (a genetic disorder)

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§ 3--Compact Bone (Fig. 7.4)A.Periosteum (C.T.) wraps around bones

B.Osteon, basic structural unit of compact bone, includes:– a central canal (vascular canal)– joined by

transverse passages called perforating canals; what inside these canals?

– concentric lamellae, from lamella to lamella are right- and left-handed helices of collagen fibers

C. Not all of the matrix is organized into osteons. Circumferential lamellae— run parallel to the bone surface

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Next Slide

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§ 4--Spongy BoneA. Sponge like appearance formed by

plates of bone called Trabeculae– Space– filled with ______________

B. Trabeculae have few osteons or central canals; Why?

– B/C no osteocyte is very far from blood of bone marrow

C. Provides strength with little weight– trabeculae (not randomly arranged) develop

along bone’s lines of stress (Fig. 7.5)

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§ 5--Bone Marrow• Def.– soft tissue that occupies the marrow

cavity of a long bone, the spaces amid the trabeculae of spongy bone, and the larger central canals. Two kinds: (Fig. 7.6)

1. Red marrow-- looks like thick blood– Consists of reticular fibers (cells), immature

blood cells, adipocytes– Function? Hemopoietic– produce blood cells

2. Yellow marrow– from red bone marrow– Contains fatty tissue– No longer produces blood cells

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Figure 7.7Fig. 7.6--Distribution of red and yellow bone marrow

Q. Where would be the most accessible places to draw red bone marrow from an adult?

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Skip section 7.3 (Bone Development;

pp. 214-219)

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III—7.4. Physiology of Osseous Tissue

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§ 7.4A. Mineral deposition

1. Mineralization/calcification – definition: crystallization process in which calcium, phosphate, . . .

– What is deposited? Calcium, phosphate, .– When? Fetal life . . . – By what cells?

2. Ectopic ossification– include arteriosclerosis and calculus (“little stone”)

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§ 7.4B. Mineral resorption1. Mineral resorption – definition: The

process of dissolving bone– By what bone cells?– Mechanism of mineral resorption–

• Calcium receptor, hydrogen pumps, and chloride ions channels present

• Hydrochloric acid dissolves the bone minerals and acid phosphatase digests the collagen

– Application– orthodontic appliances (braces) to reposition teeth

Fig. X & Y (osteoclasts), Z (braces)

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Next Slide

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Acid phosphatase

Orthodontic braces

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§ 7.4C. Calcium Homeostasis1. Calcium is important– neuron action

potentials, muscle contraction, blood clotting, exocytosis, 2nd messenger etc.

2. (Location) Where is calcium deposited to & withdrawn from?

3. Calcium in the blood—ionized form (Ca+2) or is bound to solutes (proteins etc.)– Hypocalcemia– calcium deficiency– Hypercalcemia– a blood calcium excess– (see the next slide for details)

IV-- 7.4D. Calcium homeostasis by three hormones–

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-- calcitriol -- calcitonin -- parathyroid hormone (PTH)

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§ 7.4D. Calcium and calcitriol1. Calcitriol (the most active form of vitamin D)–

synthesis (see Fig. 7.14)– Keratinocytes-- 7-dehydrocholesterol to vitamin D3– The liver-- coverts vitamin D3 to calcidiol– The kidney-- converts calcidiol to calcitriol

2. Function of calcitriol—Raise blood calcium; How?

– (where?) _________________– calcium & phosphate absorption

– Bone resorption– calcium resorption – Kidneys– reabsorption of calcium

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§ 7.4D. Calcium and calcitonin

1. Calcitonin – synthesis– By ________ (clear cells) of thyroid gland– Calcitonin is secreted when blood calcium

concentration rises too high

2. Function of calcitonin— lowers blood calcium; How? On bones:

– Osteoclast inhibition– reduces osteoclast activity; less calcium is liberated from bones

– Osteoblast stimulation– results in calcium deposition

– Fig. 7.16a

secretion

❶Blood ca+2 excess

❷ Blood ca+2 returns to normal

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§ 7.4D. Calcium and PTH1. Parathyroid hormone (PTH)– synthesis

– By the ____________ glands, located at the posterior surface of the thyroid gland

– PTH is secreted when blood calcium concentration is low

2. Function of parathyroid hormone (PTH)— raises blood calcium level; How? On bones and kidneys

– Osteoclast stimulation– promotes osteoclast activity; more calcium is liberated from bones

– Osteoblast inhibition– results in less calcium deposition– Kidneys– PTH promotes calcium reabsorption by the

kidneys; PTH also promotes calcitriol synthesis in kidneys

– Fig. 7.16b

secretion

❶Blood ca+2 too low

❷ Blood ca+2 returns to normal

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V– 7.5 on Osteoporosis; read p. 228 in the textbook

(Deeper Insight 7.4)

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Skip section 7.5 (Bone disorder;

pp. 225-227)

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1. Symptoms– bones lose mass, become brittle etc.

2. Causes— aging, bone resorption3. Results– fractures, kyphosis etc.4. Diagnosis– X rays to measure bone density5. Treatments– estrogen (is out of favor), bis-

phosphonates etc. 6. Prevention– between the ages of 25-40;

exercise and a good bone-building diet– 4 Figures– Watch a video when available (also on the

publisher’s website)

§ 7.5. Osteoporosis

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Figure 7.22a

Sponge bone in the body of vertebra in good health (Left) and with osteoporosis (Right)

Left Right

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Lumbar vertebrae severely damaged by osteoporosis

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Kyphosis (widow’s hump)

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Questions (muddiest points)?

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