1. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings BIOLOGY OF HUMAN AGING The Skeletal System CHAPTER 5

2. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Outline 1.Review of Structure and Function Bone / Cartilage 2. Age-related changes 3. Age-related dys-functions Bursitis Arthritis Osteoarthritis Rheumatoid Arthritis Gouty Arthritis Ostoporosis Tumors of Bone

3. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Function of Bones 1.Supportframework 1.Support – form the framework that supports the body soft tissues/organs, points of attachment for muscles protective casebrain, spinal cord,vital organs, heart, lung (skull, vertebral column, rib cage) 2.Protection – provide a protective case for the brain, spinal cord, and vital organs, heart, lung (skull, vertebral column, rib cage) 3.Movementmuscles 3.Movement – provide levers for muscles mineralscalcium Na, K, pahosphorus (strength & firmness of bones) 4.Mineral storage – reservoir for minerals, especially calcium Na, K, and pahosphorus (strength & firmness of bones) hematopoiesisred 5.Blood cell formation – hematopoiesis occurs within the red marrow tissue of certain bones

4. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Review of Structure and Function Bone Textures Various bone groups in the skeletal system: short, flat, irregular & long bones Long bone: shaft Compact bone Compact bone – dense outer layer Spongy bone Spongy bone – honeycomb of trabeculae filled with yellow bone marrow

5. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Structure of Long Bone Long bones consist of a shaft (diaphysis) and two ends (epiphysis) Diaphysis (yellow BM cavity)Central medullary cavity (yellow BM cavity) Tubular shaft that forms the axis of long bones Composed of compact bone that surrounds the medullary cavity Yellow BM (fat stirage) is contained in the medullary cavity

6. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Structure of Long Bone Epiphyses Expanded ends of long bones compact bonespongy bone Exterior is compact bone, and the interior is spongy bone Red BM (site of hematopoiesis)Spongy bone contains Red BM (site of hematopoiesis) (hyaline) Joint surface is covered with articular (hyaline) cartilage diaphysis epiphyses Epiphyseal line separates the diaphysis from the epiphyses

7. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Structure of Long Bone Figure 6.3

8. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Compact Bone (microscopic examination) Haversian system or osteon – the structural unit of compact bone (interconnecting canals) Lamella – weight-bearing, column-like matrix tubes composed mainly of collagen Lacunae: Lacunae: small cavities b/w adjacent lamellae (contains bone forming cells); canaliculi interconnect lacunae w/in haversian system Haversian, or central canal – central channel containing blood vessels and nerves

9. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Structure of Bone: Compact Bone Osteocytes – mature bone cells Lacunae – small cavities in bone that contain osteocytes Canaliculi – hair-like canals that connect lacunae to each other and the central canal, allow passage of nutrients and waste b/w osteocytes

10. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Structure of Bone: Compact Bone Figure 6.6a, b

11. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Chemical Composition of Bone: Organic Osteoblasts – bone-forming cells Osteocytes – mature bone cells Osteoclasts – large cells that resorb or break down bone matrix

12. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Chemical Composition of Bone: Inorganic Mineral salts Sixty-five (65%) percent of bone by mass Mainly calcium phosphates Responsible for bone hardness and its resistance to compression

13. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Bone Development Osteogenesis and ossification – the process of bone tissue formation, which leads to: The formation of the bony skeleton in embryos Bone grows until early adulthood Bone thickness, remodeling, and repair

14. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Factors influencing bone development 1.Stress Bone is a living tissue, capable of undergoing structural changes; Bone subjected to heavy loads for prolonged periods  increased deposition of collagen fibers & inorganic salts Types of stress Gravity Functional forces (when contracting muscles) 2. Interaction of two hormones play a role in bone development

15. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Control of Remodeling Hormonal mechanism maintains calcium homeostasis in the blood

16. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Hormonal Regulation of Bone Development Rising blood Ca 2+ Rising blood Ca 2+ levels trigger the thyroid gland to release calcitonin Calcitonin stimulates calcium salt deposit in bone (new bone) Falling blood Ca 2+ Falling blood Ca 2+ levels signal the parathyroid glands to release PTH PTH signals osteoclasts to degrade bone matrix and release Ca 2+ into the blood Nutrition greatly influences bone development; mainly Vit. D

17. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Regulation of bone development by hormones Figure 6.12

18. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Skeletal Cartilage Various types of cartilage (based on fiber content & matrices) hyaline, elastic, and fibro-cartilage Like bone; cartilage is composed of matrix in which cells are embedded in lacunae, also matrix is mostly collagenous fibers chondrocytes chondrin Unlike bone; cartilage matrix is not organized into Haversian system, instead randomly scattered cells called chondrocytes, no Ca or P, chondrin (protein and carbohydrate)

19. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Cartilage … no blood vessels in cartilage In contrast to bone, no blood vessels in cartilage Blood supply: blood vessels located in surrounding connective tissue Survival of chondrocytes depends on diffusion (not efficient) Chondrocytes metabolically less active than ostocytes, takes longer to heal upon injury

20. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Hyaline Cartilage Provides support, flexibility, and resilience Is the most abundant skeletal cartilage Is present in these cartilages: a. Covers the ends of long bones b. Costal – connects the ribs to the sternum c. Nasal – supports the nose

21. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Elastic Cartilage elastic fibers Similar to hyaline cartilage but contains elastic fibers external ear Found in the external ear

22. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Fibrocartilage tensileHighly compressed with great tensile strength collagenContains collagen fibers meniscus of the knee intervertebral discsFound in meniscus of the knee and in intervertebral discs

23. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Growth of Cartilage Interstitial – lacunae -- bound chondrocytes inside the cartilage divide and secrete new matrix, expanding the cartilage from within Calcification of cartilage occurs: 1.During normal bone growth 2.During old age

24. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Bones and Cartilages of the Human Body Figure 6.1

25. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Age-related changes major age-related change Loss of calcium from bone (more in female than male) [major age-related change] Collegen fibers decreases (due to decreased protein synthesis) Gradual increase of inorganic salts in the bone matrix (bone may become brittle and fracture easily due to increased mineral salts) Medullary cavity of long bones become enlarged due to bone resorption Decrease ability of bone to withstand stress w/ aging (due to loss of collagen fibers) Bones become thinner Bone formation vs. bone resorption (higher osteoclast or lower osteoblast activity) Hormonal imbalance (parathyroid hormone and calcitonin), sclerotic blood vessel Joints become thinner and signs of deterioration may appear Restriction of movement of joints Calcification of costal cartilage (large joint b/w ribs & sternum)  restrict flexibility Changes in the fibrocartilage that forms the intervertebral discs of spinal column Center of each disc is known as nucleus pulposus (gradual loss of water & cells) Formation of lipofucin and calcification of the discs and other degenerative processes may occur (back problems in lumbar & cervical regions) Deformity of the vertebral column or poor posture

26. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Age-related Dysfunction Bursitis: bursae small fluid filled sacs lined with synovial membrane, act as cushion located around joints between tendons and bones, reduce friction between these structures. bursitis Inflammation (injury, exercise, infection, crystal deposition) of bursae is called bursitis, mainly in shoulder joint

27. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Arthritis: various types of joint inflammation or degenerative changes, more common in older persons, pathological changes, joint swelling and painful movement Osteoarthritis: most common form, chronic inflammation, gradual degeneration of cartilages on bone ends, also referred to as degenerative joint disease

28. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Age-related Dysfunction …. Rheumatoid arthritis: begins at any age, more debilitating with age, severely damages affected joints (small: hands, feet, ankles, and wrist), more common in women. Begins with the inflammation of synovial membrane, leads to swollen and thickened joint.

29. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Age-related Dysfunction …. Gouty arthritis: inherited condition, excess uric acid build up in blood, byproduct of purine breakdown, excreted from kidney, formation of sodium urate crystals in soft tissues and joints inflammatory response in great toe, wrist, elbow, knee, or ankle, cause severe pain and swelling. Cyclic symptoms, similar to RA, morning stiffness, and aching joints, more common in men.

30. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Osteoporosis reabsorption depositGroup of diseases in which bone reabsorption outpaces bone deposit Spongy boneSpongy bone of the spine is most vulnerable postmenopausalOccurs most often in postmenopausal women fragileBones become so fragile that sneezing or stepping off a curb can cause fractures