Types of Bones. 5 basic types of bones: Sutural bones - in joint between skull bones

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1 The Skeletal System

2 The Skeletal System Bone and their cartilage, ligaments & tendons. Dynamic and ever changing throughout life Skeleton contains all 4 tissue types; Epithelial, connective, muscle and nerve The bone itself is formed by connective tissue and contains other connective tissue such as adipose (fat) tissue, blood cells, cartilage and dense connective tissue

3 Functions of Bone 1. Supporting & protecting soft tissues 2. Attachment site for muscles making movement possible 3. Storage of the minerals, calcium & phosphate -- mineral homeostasis 4. Site of blood cell production in the bone marrow (hemopoiesis) 5. Energy storage in yellow marrow(fat)

4 5 basic types of bones: 1. Long - greater length than width 2. Short - same length and width 3. Flat 4. Irregular variable shape 5. Sesamoid covered in tendons or ligaments (patella) Sutural bones - in joint between skull bones Types of Bones

5 Anatomy of a Long Diaphysis - shaft Bone Epiphysis - one end of a long bone Metaphysis - growth plate region Articular cartilage over joint surfaces acts as friction & shock absorber Medullary cavity - marrow cavity Endosteum - Epithelial lining of marrow cavity containing osteoblasts & osteoclasts (bone resorbing cells) Periosteum - tough membrane covering bone but not the cartilage - outer fibrous layer - dense irregular connective tissue -innerosteogenic layer - bone cells & blood vessels that nourish and help with repairs

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9 Histology of Bone A type of connective tissue as seen by widely spaced cells separated by matrix (more matrix than cells) Matrix composed of 15% water 30% collagen fibers 55% crystalized mineral salts (hydroxyapatite which is mainly Ca 3 (PO 4 ) 2 Ligaments & tendons attach to periosteum

10 Matrix of Bone Inorganic mineral salts provide bone s hardness Hydroxyapatite (Calcium-Phosphate) / Calcium carbonate / Fluoride/Sulfur Organic collagen fibers provide bone s flexibility resists being stretched or torn remove minerals with acid & rubbery structure results Mineralization (calcification) is hardening of tissue when mineral crystals deposit around collagen fibers Bone is not completely solid since it has small spaces for vessels and red bone marrow spongy bone has many spaces compact bone has very few spaces

11 Compact Bone Also called cortical bone Looks like solid hard layer of bone Makes up the shaft of long bones and the external layer of all bones Resists stresses produced by weight and movement Composed of repeating units called osteons or haversian systems.

12 Histology of Compact Bone Osteon is concentric rings called lamellae of calcified matrix surrounding a central canal of a blood vessel Osteocytes found in spaces called lacunae (little lakes) Osteocytes communicate through canaliculi filled with extracellular fluid that connect one cell to the next cell

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14 Spongy Bone Also called cancellous or trabecular bone Located on the interior protected by compact bone Lamellae arranged in an irregular pattern of thin columns called trabeculae Spaces between trabeculae filled with yellow or red bone marrow Located in regions where bones are not heavily stressed or where stresses are distributed

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16 No true Osteons. The Trabeculae of Spongy Bone Latticework of thin plates of bone called trabeculae Lamella are not in concentric rings Spaces in between these struts are filled with red marrow where blood cells develop Found in ends of long bones and inside flat bones such as the hipbones, sternum, sides of skull, and ribs.

17 Compact vs. Spongy Bone Compact Bone Also called cortical bone. Arranged in osteons composed of concentric lamellae Osteocytes reside in lacuna Has central (Haversion) and perforating (Volksmann) canals for blood vessels Supportive & dense Found on outside of bone Spongy Bone Also called cancellous or trabecular bone No true osteons; each trabecula has nonconcentric lamellae Osteocytes reside in lacuna Nutrients supplied by red marrow that fills in spaces between trabeculae Non supportive & less dense Only found on inside of bones

18 4 Cells Associated With Bone 1. Osteogenic cells - undifferentiated stem cells can divide to replace themselves & can become osteoblasts found in inner layer of periosteum and endosteum 2. Osteoblasts-form matrix & collagen fibers but can t divide 3. Osteocytes-mature cells that no longer secrete matrix 4. Osteoclasts- huge cells from fused monocytes (WBC) function in bone resorption / increase blood calcium

19 2 Patterns of Bone Formation 1. Intramembranous ossification - the bone forms / originates between sheet like layers of connective tissue / ex. flat bones of skull 2. Endochondral Ossification - ossification / replacement of a hyline cartilage model with bone / ex. long bones

20 Embryo Fetus Newborn A fetal skeleton is mostly connective tissue that is gradually replaced with bone beginning at 6 weeks of development Adult

21 Bone Growth in Length Epiphyseal Plate or Cartilage Growth Plate cartilage cells are produced by mitosis on epiphyseal side of plate cartilage cells are destroyed and replaced by bone on diaphyseal side of plate Between ages 18 to 25 the epiphyseal plates close. cartilage cells stop dividing and bone replaces the cartilage (epiphyseal line) Growth in length stops by age 25

22 Bone Growth in Width Only by appositional growth at the bone s surface Periosteal cells differentiate into osteoblasts and form bony ridges and then a tunnel around periosteal blood vessel. Concentric lamellae fill in the tunnel to form an osteon.

23 Bone Remodeling Throughout life, the process of bone remodeling replaces old bone tissue with new bone tissue. Involves bone remodeling & bone deposition 5% of bone is being remodeled at any time 4% of total compact bone per year and 20% of spongy bone per year is remodeled.

24 Bone Remodeling Removed injured bone Bone grows thicker and stronger in response to stress Shape can be altered for proper support

25 Factors Affecting Bone Growth Nutrition vitamin D for calcium absorption calcium and phosphorus for bone growth vitamin C for collagen formation vitamins K and B12 for protein synthesis Sufficient levels of specific hormones sex steroids at puberty growth spurt and closure of the epiphyseal growth plate estrogens promote female changes -- wider pelvis

26 Hormones Affecting Homeostasis of Bone 1. Human Growth Hormone (hgh) - general growth of all body tissues including bone 2. Sex Hormones / Estrogen & Testosterone - increases osteoblast activities (steroids) 3. Insulin & Thyroid hormones - promotes normal bone & body growth 4. Parathyroid Hormone (PTH) - increases osteoclast activity leading to bone resorption and increase blood calcium 5. Calcitonin - hormone from thyroid gland that increases the deposition of calcium by osteoblast and thus lowering blood calcium level See Diagram

27 epiglottis thyroid cartilage (Adam s apple) pharynx blood vessel THYROID GLAND trachea (windpipe) PARATHYROID GLANDS

28 Calcium Homeostasis & Bone Tissue Skeleton is reservoir of calcium & phosphate Calcium ions involved with many body systems nerve & muscle cell function blood clotting enzyme function in many biochemical reactions Small changes in blood levels of Calcium can be deadly (plasma level maintained 9-11mg/100mL) cardiac arrest if too high respiratory arrest if too low

29 Hormonal Influences Parathyroid hormone (PTH) is secreted if Blood Calcium level falls PTH gene is turned on & more PTH is secreted from gland osteoclast activity increased, kidney retains calcium and produces calcitriol (active form of vitamin D) Thus PTH increases blood calcium levels Calcitonin hormone is secreted from parafollicular cells in thyroid gland if Blood Calcium level gets too high inhibits osteoclast activity increases bone formation by osteoblasts Thus Calcitonin decreases blood calcium levels

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31 Hormonal Abnormalities 1. Gigantism - oversecretion of hgh during childhood produces giantism / cartilage cells at epiphyseal plate continue to divide 2. Acromegaly - over secretion of hgh after growth plates have closed (adult) / thick joints 3. Under secretion of hgh or thyroid hormone during childhood produces short stature 4. Parathyroid gland tumor - bone resorption and high blood calcium

32 age 9 age 16 age 33 age 52

33 Fractures Named for shape or position of fracture line 1. Partial - break across bone is incomplete 2. Complete - bone completely broken 3. Closed -- no break in skin 4. Open fracture --skin broken 5. Comminuted -- broken ends of bones are fragmented 6. Greenstick -- partial fracture 7. Impacted -- one side of fracture driven into the interior of other side 8. Stress fracture -- microscopic breaks

34 Fracture & Repair of Bone Fracture is break in a bone Healing is faster in bone than in cartilage due to lack of blood vessels in cartilage Healing of bone is still slow process due to vessel damage(hematoma) Clinical treatment closed reduction = restore pieces to normal position by manipulation open reduction = surgery to set

35 Repair of a Fracture (1) 1. Formation of fracture hematoma damaged blood vessels produce clot in 6-8 hours, bone cells die inflammation brings in phagocytic cells for clean-up duty new capillaries grow into damaged area 2. Formation of fibrocartilagenous callus formation fibroblasts invade the procallus & lay down collagen fibers chondroblasts produce fibrocartilage to span the broken ends of the bone

36 Repair of a Fracture (2) 3. Formation of bony callus osteoblasts secrete spongy bone that joins 2 broken ends of bone lasts 3-4 months 4. Bone remodeling compact bone replaces the spongy in the bony callus surface is remodeled back to normal shape

37 Exercise & Bone Tissue Pull on bone by skeletal muscle and gravity is mechanical stress Stress increases deposition of mineral salts & production of collagen (calcitonin prevents bone loss) / Use it or Loose it Lack of mechanical stress results in bone loss reduced activity while in a cast astronauts in weightlessness (1% loss per week) bedridden person Weight-bearing exercises build bone mass (walking or weight-lifting)

38 Aging & Bone Tissue Bone is being built through adolescence, holds its own in young adults, but is gradually lost in aged. Demineralization = loss of minerals very rapid in women as estrogens levels decrease in males, begins after age 60 Decrease in protein synthesis decrease in growth hormone decrease in collagen production which gives bone its tensile strength bone becomes brittle & susceptible to fracture

39 Osteoporosis Decreased bone mass resulting in porous bones Those at risk white, thin menopausal, smoking, drinking female with family history athletes who are not menstruating due to decreased body fat & decreased estrogen levels people allergic to milk or with eating disorders whose intake of calcium is too low Prevention or decrease in severity adequate diet, weight-bearing exercise, & estrogen replacement therapy (for menopausal women) behavior when young may be most important factor Estrogen - with decrease estrogen as during menopause then increased osteoclast activity and decreased osteoblast activity

40 Rhumatism and Arthritis Rheumatism - general term for a variety of painful disorders of the supporting structures / bones, ligaments, tendons, and muscles Arthritis - many different diseases characterized by inflammation of one or more joints / pain from inflammation / a form of rheumatism / 3 classes of arthritis

41 3 Classes / Types of Arthritis 1. Diffuse CT Disease ex. Rhumatoid Arthritis (RA) autoimmune disease attacks cartilage lining small joints joints / bilateral pannus(granulation) formed / joint becomes fused and distorted

42 2. Osteoarthritis Degenerative joint disease / cartilage wears wear and tear and age related deterioration of joint cartilage affects large joints / not bilateral spurs(bumps) of bone form on exposed surfaces of cartilage size of joint space is reduced / stiff and limited movement

43 3. Gouty Arthritis Metabolic disorder uric acid builds up in the body problem with protein metabolism forms sodium urate deposits to build up in kidneys, ear cartilage & joints causes inflammation of joints