Chapter 7 Bone Tissue 7 1 Ch 7

Chapter 7– Bone Tissue 7 -1

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. 220224) 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 7 -2

§ 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 7 -3

I-- 7. 1. Introduction 7 -4

§ 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 7 -5

§ 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 7 -6

§ 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 7 -7

§ Structures of long bones (A)-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 7 -8

2 4 -6 1 7 -10 3 7 -9

§ Structures of long bones (B)-1. Epiphyseal plate (growth plate; in children)— What is it? 2. Epiphyseal line (in adults)— Fig. X and Y 7 -10

In children 7 -11

An adult bone 7 -12

§ Flat Bone of the Cranium 1. 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 7 -13

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Match the following bones to these four bone shapes A. Long bone B. Short bone C. Flat bone D. Irregular bone 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 7 -15

II-- 7. 2. Histology of Osseous Tissue 7 -16

§ 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 7 -17

§ 1 --Four Types of Bone Cells (2) 4. Osteoclasts (bone-dissolving cells) develop in bone marrow by fusion of 350 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. 4 b 7 -18

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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. 7 -20

§ 2 --Matrix of Osseous Tissue • Dry weight = 2/3 inorganic; 1/3 organic matter 1. 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 adults 2. 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) 7 -21

Rickets 7 -22

Also called-Osteogenesis imperfecta (a genetic disorder) 7 -23

§ 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 7 -24 parallel to the bone surface

Next Slide 7 -25

§ 4 --Spongy Bone A. 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) 7 -26

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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 7 -28

Fig. 7. 6 -Distribution of red and yellow bone marrow Figure 7. 7 Q. Where would be the most accessible places to draw red bone marrow from an adult? 7 -29

Skip section 7. 3 (Bone Development; pp. 214 -219) III— 7. 4. Physiology of Osseous Tissue 7 -30

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§ 7. 4 A. 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”) 7 -32

§ 7. 4 B. Mineral resorption 1. 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) 7 -33

Next Slide 7 -34

Acid phosphatase 7 -35

Orthodontic braces 7 -36

§ 7. 4 C. Calcium Homeostasis 1. Calcium is important– neuron action potentials, muscle contraction, blood clotting, exocytosis, 2 nd 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) 7 -37

IV-- 7. 4 D. Calcium homeostasis by three hormones– -- calcitriol -- calcitonin -- parathyroid hormone (PTH) 7 -38

§ 7. 4 D. Calcium and calcitriol 1. Calcitriol (the most active form of vitamin D)– synthesis (see Fig. 7. 14) – – – Keratinocytes-- 7 -dehydrocholesterol to vitamin D 3 The liver-- coverts vitamin D 3 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 7 -39

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§ 7. 4 D. 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. 16 a 7 -41

❷ Blood ca+2 returns to normal ❶ Blood ca+2 excess secretion 7 -42

§ 7. 4 D. Calcium and PTH 1. 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 7 -43 Fig. 7. 16 b

❷ Blood ca+2 returns to normal ❶ Blood ca+2 too low secretion 7 -44

Skip section 7. 5 (Bone disorder; pp. 225 -227) V– 7. 5 on Osteoporosis; read p. 228 in the textbook (Deeper Insight 7. 4) 7 -45

§ 7. 5. Osteoporosis 1. Symptoms– bones lose mass, become brittle etc. 2. Causes— aging, bone resorption 3. Results– fractures, kyphosis etc. 4. Diagnosis– X rays to measure bone density 5. Treatments– estrogen (is out of favor), bisphonates 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 -46

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Sponge bone in the body of vertebra in good health (Left) and with osteoporosis (Right) Figure 7. 22 a Left Right 7 -48

Lumbar vertebrae severely damaged by osteoporosis 7 -49

Kyphosis (widow’s hump) 7 -50

Questions (muddiest points)? 7 -51