BIO121 Week 8 Lecture Notes
BIO121 Week 8 Lecture Notes Bio 121
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This 4 page Class Notes was uploaded by BenWilliams on Sunday October 16, 2016. The Class Notes belongs to Bio 121 at Parkland College taught by Erbach in Fall 2016. Since its upload, it has received 6 views. For similar materials see Anatomy and Physiology in Natural Sciences at Parkland College.
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Date Created: 10/16/16
Week 8 Lecture Notes 10/10-10/14 I. Functions of the Skeletal System A. Support- forms framework for body B. Protection- surrounds vital organs C. Movement- bones are levers for muscles to use D. Hematopoiesis- blood cell formation E. Mineral Storage II. Types of Bones A. Sutural Bones 1. Located between flat bones of the skull B. Flat Bones 1. Thin parallel surfaces a) Ribs, scapula, sternum C. Short Bones 1. Box-like appearance a) Carpals, tarsals D. Long Bones 1. Longer than they are wide a) Humerus, femur E. Irregular Bones 1. Have notches and ridges a) Vertebrae, pelvis F. Sesamoid Bones 1. Develop inside tendons a) Patella III. Bone Features List A. Projections- places for tendons, ligaments, or articulations 1. Head 2. Diaphysis 3. Tubercle 4. Tuberosity 5. Trochlea 6. Condyle 7. Trochanter 8. Facet 9. Crest 10. Line 11. Spine 12. Ramus B. Depressions- places for blood vessels or nerves to pass 1. Canal/Meatus 2. Spinus 3. Foramen 4. Fissure 5. Sulcus 6. Fossa IV. Long Bones A. Epiphysis 1. Expanded area at end of bone 2. Mostly spongy bone 3. Articular cartilage covers part of epiphysis B. Metaphysis 1. Connects epiphysis to shaft C. Diaphysis 1. Shaft of bone 2. Wall has thick layer of compact bone 3. Medullary cavity inside a) Red marrow- red blood cell production b) Yellow marrow- adipose tissue (energy reserve) D. Periosteum 1. Protective outer covering made with fibrous connective tissue E. Endosteum 1. Covers all internal cavities 2. Made from thin connective tissue with stem cells (osteogenic cells) F. Vascular Features 1. There is a nutrient artery and vein in all long bones 2. Nutrient foramen a) Opening for blood vessels V. Flat Bones A. Layer of compact bone on outside B. Spongy bone in middle 1. Basically a sandwich… VI. Bone Cell A. Osteocyte 1. Main bone cell type that cannot divide B. Osteoblast 1. Creates new boney matrix 2. This is an immature osteocyte while it is secreting the matrix C. Osteoclast 1. Bone reabsorption 2. Releases acids and enzymes to dissolve the matrix a) Osteolysis 3. Large and multinucleated D. Osteogenic Cells 1. Mitotic stem cells in endosteum and periosteum 2. Differentiate into osteoblasts VII. Compact vs. Spongy Bone A. Compact (Lamellar or Cortical) 1. Dense, solid, no gaps, heavy 2. Made by many osteons 3. Forms diaphysis and all bone surfaces B. Spongy (Cancellous or Trabecular) 1. Forms where not much stress occurs 2. Reduces skeletal weight VIII. Osteogenesis A. Intramembranous Ossification 1. Begins in 8th week of development 2. Bones forming without a cartilage template 3. Mesenchymal stem cells differentiate directly into osteoblasts B. Endochondral Ossification 1. Initial skeleton formed by hyaline cartilage 2. Cartilage is gradually replaced by bone tissue C. Layers Long Bone Elongation (Inside → Outside) 1. Proliferation Zone a) Cartilage cells undergo mitosis 2. Hypertrophic Zone a) Cartilage cells enlarge 3. Calcification Zone a) Matrix calcifies b) Chondrocytes die c) Blood vessel begin to occupy chondrocyte lacunae 4. Ossification Zone a) New bone matrix forms 5. Note that long bone elongation ceases at some point in development D. Appositional Growth (Width) 1. This type of growth can occur throughout life 2. When osteoblasts widen the bone by creating more matrix, osteoclasts will increase the medullary cavity E. Bone Growth Hormones 1. Growth Hormone- stimulate epiphyseal plate in early life 2. Thyroid Hormone- controls growth hormone 3. Testosterone/Estrogen- stimulate growth during puberty IX. Bone Remodeling A. Deposit 1. Osteoblasts secrete osteoid (collagen fibers that wrap around osteon) 2. Mineral salts accumulate around fibers B. Reabsorption 1. Osteoclasts dig depressions in matrix 2. Secrete enzymes and acid (H+ ions) to dissolve matrix a) Acid converts the salts into soluble products to be absorbed into the blood 3. Undergo apoptosis once enough bone is dissolved C. Hormonal Control 1. Blood needs to maintain Ca levels a) This is a negative feedback loop 2. Absorption of Ca requires vitamin D X. Calcium Regulating Hormones A. Parathyroid Hormone- increases blood Ca levels 1. Osteoclasts release stored Ca from bone matrix 2. Intestines absorb more Ca from diet 3. Kidneys reabsorb Ca from urine by releasing calcitriol (vitamin D) B. Calcitonin- decreases blood Ca levels 1. Osteoclast activity inhibited 2. Intestinal Ca absorption decreases 3. Inhibits kidney release of calcitriol (vitamin D) It was at this moment in lecture that I realized vitamin D is a hormone called calcitriol…
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