Chapter 6, 7, 8: Skeletal System PDF

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Chapter 6, 7, 8: Skeletal System...

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Chapter 6, 7, 8

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Chapter 6, 7, 8: Skeletal System Functions of Skeletal System •

Support;

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Protection;

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Movement;

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Store minerals and lipids;

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Produce blood cell;

Axial and Appendicular Skeleton •

Axial includes:

- Skull, thorax, vertebral column. •

Appendicular includes:

- Limbs, pectoral, pelvic. 6 Types of Bones •

Flat bones

- Thin with parallel surface - Ex: Bones of the skull roof, sternum, ribs, scapulae. - They provide protection for underlying soft tissues and offer an extensive surface area for the attachment of skeletal muscles. •

Sutural

- Small, flat, irregularly shaped bones. - Between flat bone of the skull. - Number varies among individuals. •

Long

- Long and slender - Found in arms, forearm, legs, thigh, fingers, palms, soles, toes. - Femur is the longest and heaviest bone in the body.

Chapter 6, 7, 8 • Irregular

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- Have complex shapes with short, flat, notched, or ridged surface. - Ex: Spinal vertebrae, pelvic bones. •

Sesamoid

- Small, round, flat. - Found near joints of the knees, hands, feet. - Few people have sesamoid bones at every possible location. - Everybody has sesamoid patellas (kneecaps) •

Short

- Boxy. - Ex: Carpal bones, tarsal bones. Male & Female Pelvis

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Structure

Male

Femal

Bone

Heavy and thick

Light and thin

Pelvis brim (inlet)

Smaller and heart-shaped

Larger and oval

Sacrum

Longer, narrower, more curved anteriorly

Shorter, less curved anteriorly

Coccyx

Less movable

More movable

Pubic arch angle

90

Female pelvis has evolved to its maximum width for childbirth

Bone Cells (the organic components of bone tissue the inorganic component is mineral salts) •

Make up only 2% of bone mass.

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Osteogenic cells

- Mesenchymal cells (stem cells) that divide to produce osteoblasts. - Located in inner cellular layer of periosteum and in endosteum. - Assist in fracture repair. •

Osteoblasts

Chapter 6, 7, 8 - Bone-forming cells.

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- Lay down bone matrix and collagen fibers. - They will mature into osteocytes. •

Osteocytes

- Mature bone cells that do not divide. - Live in lacunae between layers of matrix. - Have cytoplasmic extensions that pass through canaliculi. - 2 major functions: i.

Maintain protein and mineral content of matrix;

ii. Help repair damaged bone. •

Osteoclasts (Bone destroying cells)

- Responsible for bone resorption. - Large, multinucleate cells. - Break down bone for remodeling and release of calcium. Compact Bone Osteon •

The functional unit of compact bone.

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Central canal

- Contains blood vessels. •

Perforating canals

- Perpendicular to surface of bone. - Carry blood vessels into deep bone and marrow. •

Lacunae are cavities that surround osteocytes, forming concentric rings (lamellae) around the central canal

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Lamellae (Layers of bone matrix)

- Concentric lamellae surround central canal. - Interstitial lamellae fill spaces between osteons. - Circumferential lamellae are at outer and inner bone surface.

Chapter 6, 7, 8

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Spongy Bone •

Lacks osteon.

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Composed of trabeculae that contain the osteocytes. Red marrow (in adults, it’s found in flat bones, epiphyses of femur and humerus)fills the spaces.

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Located in epiphyses of long bones, ribs, vertebra and skull bones.

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Yellow bone marrow

- Stores fat. - In adults, it is found in medullary cavity of long bones. •

Bone marrows are primarily located in the ribs, vertebrae, sternum, pelvis.

Compact bones are good at handling weight, spongy bones & are good at handling forces from multiple directions, together, they make bone really tough.

Anatomy of A Long Bone •

Diaphysis (shaft)

- Wall of compact bone. - Central space called medullary cavity. •

Epiphysis

- Mostly spongy bone •

Metaphysis

- Where diaphysis & epiphysis meet. •

Periosteum

- Membrane that covers outside of the bone. - Made of fibrous connective tissue membrane. •

Endosteum

- Active during bone growth, repair, remodeling. - Covers trabeculae of spongy bone. - Line central canal of compact bone.

Chapter 6, 7, 8 - Consists of flatted layer of osteogenic cells. •

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Articular cartilage

- Hyaline cartilage covers the external surface of the epiphysis. - Decreases friction at joint surfaces. •

Medullary cavity

- Contains yellow marrow in adults. - Contains red marrow in infants. Bone Ossification •

Ossification

- Bone formation i.

Endochondral ossification a) How most of the bones form. b) Primary ossification center develops inside hyaline cartilage, and cartilage is gradually replaced by bone.

ii. Intramembranous ossification a) Bone develops from mesenchyme (embryonic connective tissue)

Bone Growth •

The epiphyseal plate is the area of growth in a long bone

- On the epiphyseal side of the epiphyseal plate, cartilage is formed. - On the diaphysial side, cartilage is ossified, and the diaphysis grows in length - The epiphyseal plate is composed of four zones of cells and activity: i.

Reserve zone is the region closest to the epiphyseal end of the plate and contains small chondrocytes within the matrix, and do not participate in bone growth.

ii. Proliferative zone is the next layer toward the diaphysis and contains stacks of slightly larger chondrocytes. It makes new chondrocytes (via mitosis) to replace those that die at the diaphysial end of the plate.

Chapter 6, 7, 8 6/7 iii. Zone of maturation and hypertrophy, are older and larger than those in the proliferative zone. The more mature cells are situated closer to the diaphysial end of the plate. iv. Zone of calcified matrix, the zone closest to the diaphysis, are dead because the matrix around them has calcified. The longitudinal growth of bone is a result of cellular division in the proliferative zone and the maturation of cells in the zone of maturation and hypertrophy. •

Appositional growth

- An increase in diameter - Growth in diameter can continue even after longitudinal growth ceases. •

Epiphyseal Plate to Epiphyseal Line

- Epiphyseal plates are visible in a growing bone. - Epiphyseal lines are the remnants of epiphyseal plates in a mature bone. Fractures Repair •

Hematoma forms (A hematoma forms)

- Production of a large blood clot; - Establishes a fibrous network; - Bone cells in the area die. •

Callus formation

- Callus of endosteum and periosteum divide and migrate into fracture zone. - Calluses stabilize the break: i.

Internal callus develops in medullary cavity;

ii. External callus of cartilage and bones surrounds break. •

Spongy bone formation (Cartilage of the callus replaced by trabecular)

- Osteoblasts replace central cartilage of external callus with spongy bone. •

Compact bone formation (Remodeling occurs)

- Repaired bone may be slightly thicker and stronger than normal. Bone Remodeling

Chapter 6, 7, 8 • Occurs throughout life. •

Resorption of old or damaged bone takes place on the same surface where osteoblasts lay new bone to replace that which is resorbed.

Calcium Homeostasis •

Parathyroid hormones (PTH)

- Produced by parathyroid glands. - Increases blood Ca²⁺ levels by: i.

Stimulating osteoclast activity.

ii. Increasing intestinal absorption of Ca by enhancing calcitriol secretion by kidneys. iii. Decreasing Ca excretion by kidneys. •

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Calcitonin

- Secreted by C cells in thyroid. - Decreases blood Ca²⁺ levels by: i.

Inhibiting osteoclast activity.

ii. Increasing Ca²⁺ excretion and reducing calcitriol secretion by kidneys. iii. Decreasing intestinal absorption of Ca....