physiology

• Inflammation


  1. Increases permeability of blood vessels (histamine)

  2. High histamine = no way for breathing; that is why there is antihistamine

  3. Causes loss of function (lose ability to do what you are supposed to do)

  4. Symptoms: redness, heat, swelling, pain
• Bacteria in the wound make contact with defense cells (mast cells)

  Mast cells release histamine
• Histamine promotes permeability of blood vessels

  Tissue swelling
• Bacteria also attract macrophages

  Macrophages release chemical promoting dilation of capillaries: results to vasodilation > more blood > skin area becomes red and hot
• Skin as we age

  • The skin reaches its optimal appearance when we are in our twenties and thirties
  • Visible changes in the skin begin to appear as continually exposed by abrasion, chemicals, wind, sun, and other irritants
  • Pores become clogged with air pollutants and bacteria which may lead to pimples, scales, and various kinds of dermatitis or skin inflammation
• Aged skin (especially the dermis) is thinner than young skin, and the migration of cells from the basal layer to the epidermal surface slows considerably
• Changes in aged skin

  • Collagen fibers in the dermis begin to decrease in number, stiffen, break apart, and disorganize into a shapeless, matted tangle
  • Elastic fibers lose some of their elasticity, thicken into clumps, and fray, an effect that is greatly accelerated in the skin of smokers
  • Fibroblasts, which produce both collagen and elastic fibers, decrease in number
• The skin forms the characteristic crevices and furrows known as wrinkles
• Other changes in aged skin

  • Lipid content of tissues change
  • Dendritic cells decrease and become less efficient phagocytes, decreasing the skin's immune responsiveness
  • Sebaceous glands production decreases resulting in dry and broken skin that is more susceptible to infection
  • Functioning melanocytes decrease resulting in gray hair and atypical skin pigmentation
  • Hair follicles stop producing hairs, increasing hair loss
  • Nails may become more brittle with age, often due to dehydration or repeated use of cuticle remover or nail polish
• There is no way to avoid aging skin; but good nutrition, plenty of fluids, and cleanliness help delay the process
• Skeletal System and its Functions

  • Support
  • Protection
  • Assistance in Movement
  • Mineral Homeostasis (storage and release)
  • Blood Cell Production
  • Triglyceride Storage
• Bone


  Organ made up of several different tissues working together
• Skeletal System


  Entire framework of bones and their cartilages
• Osteology


  Study of bone structure and the treatment of bone disorders

  
• Functions of the Skeletal System

  • Support: Structural framework for body, Supports soft tissues, Provides attachment points for tendons of skeletal muscles
  • Protection: Protects internal organs from injury (e.g., rib cage = heart and lungs)
  • Assistance in Movement: Skeletal muscles are attached to bones; so, when they contract, they pull on bones to produce movement
  • Mineral Homeostasis (storage and release): Bone tissue takes 18% weight of the human body, Stores minerals (calcium and phosphorus) which contribute strength of bone, Stores 99% of body's calcium, Bone releases minerals into the blood to maintain mineral balances and distribute minerals to other parts of body
  • Blood Cell Production: Red bone marrow, Connective tissue that produces red and white blood cells and platelets through hemopoiesis
  • Triglyceride Storage: Yellow bone marrow, Consists of adipose cells that store triglycerides (potential chemical energy reserve)

  
• Long Bone Structure


  • Diaphysis
  • Epiphyses
  • Metaphyses
  • Articular Cartilage
  • Periosteum
  • Medullary Cavity
  • Endosteum

  
• Diaphysis


  Long, cylindrical main portion, Body or shaft, Heavy wall of compact or dense bone
• Epiphyses


  Proximal and distal ends, Wide part at each end, Articulation with other bones, Mostly spongy or cancellous bone, Covered with compact bone

  
• Metaphyses


  Regions between diaphysis and epiphyses (where they meet), Epiphyseal plate: layer of hyaline cartilage that allows diaphysis to grow in length, Epiphyseal line: resulting structure from when cartilage in epiphyseal plate is replaced
• Articular Cartilage


  Thin layer of hyaline cartilage covering part of epiphysis where bone forms a joint with another bone, Reduces bone friction and absorbs shock, Lacks perichondrium and blood vessels = limited repair of damage

  
• Periosteum


  Tough connective tissue sheath, Composed of outer fibrous layer of dense irregular connective tissue and inner osteogenic layer that consists of osteoprogenitor cells, Cells enable bone to grow in thickness, Protects bone, fracture repair, helps nourish bone tissue, attachment point for ligaments and tendons, Isolates bone from surrounding tissues, provides route for circulatory and nervous supply, Attached to underlying bone by perforating or Sharpey's fibers: thick bundles of collagen extending from periosteum into bone extracellular matrix, Rich in sensory nerves (e.g., nerves that carry pain sensations)

  
• Medullary Cavity


  Hollow cylindrical space within diaphysis, Contains fatty yellow bone marrow and blood vessels, Minimized weight of bone by reducing bony material, Long bones' tubular design provides maximum strength with minimum weight
• Endosteum


  Thin membrane that lines medullary cavity and internal spaces of spongy bone, Contains single layer of osteoprogenitor cells and connective tissue
• Bone Tissue and Bone Cells

  • Osteoprogenitor cells
  • Osteoblasts
  • Osteocytes
  • Osteoclasts
• Bone or Osseous Tissue

  Contains extracellular matrix that surrounds widely separated cells, Extracellular matrix: 15% water, 30% collagen fibers, 55% crystallized mineral salts, Most abundant: calcium phosphate (combines with another mineral salt, calcium hydroxide, to form crystals of hydroxyapatite that combine with other mineral salts and ions, Calcification: mineral salts crystallize and tissue harden, as they are deposited in the framework formed by collagen fibers of extracellular matrix, Initiated by bone-building cells called osteoblasts, Combination of crystallized salts and collagen fibers is responsible for characteristics of bone, Hardness depends on crystallized inorganic mineral salts, Flexibility depends on collagen fibers, Collagen fibers provide tensile strength, resistance to being stretched or torn apart
• Osteoprogenitor cells


  Unspecialized bone stem cells from mesenchyme (tissue from which connective tissues are form), Only bone cells to undergo cell division, Result: cells develop into osteoblasts, Found along inner osteogenic layer of periosteum, endosteum, and canals within bone that contain blood vessels
• Osteoblasts


  Bone-building cells, Bone deposition: synthesize and secrete collagen fibers and organic components needed to build extracellular matrix of bone tissue, Initiate calcification, As they are surrounded with extracellular matrix, they become trapped in their secretions, Result: become osteocytes, Secretes extracellular matrix
• Osteocytes


  Mature bone cells, Live in lacunae and are between layers of matrix, Connect by cytoplasmic extensions through canaliculi in lamallae, Main cells and maintain the bone tissue's metabolism (e.g., exchange of nutrients and wastes with blood) or bone matrix, Maintains and monitors protein and mineral content of matrix, Help repair damaged bone, Matures bone cells, Do not divide
• Osteoclasts


  Huge cells from fusion of 50 monocytes (white blood cell), Concentrated in endosteum, Plasma membrane: deeply folded into a ruffled border, Cell releases powerful lysosomal enzymes and acids that digest protein and mineral components of extracellular bone matrix, Bone resorption: breakdown of bone extracellular matrix that is part of normal development, maintenance, and repair of bone, Break downs extracellular matrix, Regulate blood calcium level

  
• Bone is not completely solid but has many small spaces between cells and extracellular matrix

  
• Regions of bone


  • Compact (80%)
  • Spongy (20%)

  
• Compact (Dense) Bone Tissue

  Few spaces, Strongest type of bone tissue, Location: beneath periosteum and makes up bulk of diaphyses of long bones, Function: protects, supports, and resists strains produced by weight and movement, Composition: Osteons or Haversian Systems: repeating structural units, Consists of concentric bone lamellae arranged around an osteonic canal, Bone lacunae: small spaces between concentric bone lamellae which contain osteocytes, Bone canaliculi: filled with extracellular fluid, radiating from bone lacunae, Connect bone lacunae with another and with osteonic canals, forming miniature system of interconnected canals, Provides routes for nutrients and oxygen to reach osteocytes and for removal wastes

  
• Spongy (Trabecular) Bone Tissue

  Cancellous bone tissue, Does not contain osteons, Location: interior of bone, protected by a covering of compact bone, Where bones are not heavily strained or where stresses are applied from many directions, Composition: Bone lamellae that are arranged in irregular pattern of thin columns called bone trabeculae (matrix forms an open network of trabeculae), Between this are spaces lined by endosteum and filled with red and yellow bone marrow (contain small blood vessels that provide nourishment to osteocytes), Precisely oriented along lines of strain, Characteristic that helps bones resist strains and transfer force without breaking, Need for locomotion for final arrangement, No blood vessels, Short, flat, and irregularly shaped bones: makes up most of the interior bone tissue, Long bones: forms core of epiphyses beneath paper-thin layer of compact bone and forms narrow rim bordering medullary cavity of diaphysis, Where hemopoiesis (blood cell production) occurs

  
• Blood and Nerve Supply of the Bone

  • Perforating Canals
  • Periosteal arteries
  • Transverse canal
  • Nutrient artery
  • Metaphyseal arteries
  • Epiphyseal arteries
  • Nutrient veins
  • Epiphyseal and metaphyseal veins
  • Periosteal veins
• Perforating Canals


  Small canals carrying small arteries from periosteum into the bone
• Nutrient artery


  Enters compact bone at an oblique angle via a hole called nutrient foramen, Passes through a small canal in compact bone of diaphysis called nutrient canal and then to medullary cavity, Divides into proximal and distal branches that course toward each end of bone

  
• Metaphyseal arteries


  Enter metaphyses of long bone, Together with nutrient artery, it supplies the red and yellow bone marrow and spongy tissue of metaphyses
• Epiphyseal arteries


  Enter epiphyses of long bone, Supply red and yellow bone marrow and spongy bone of epiphyses
• Veins that carry blood away from long bones

  • Nutrient veins
  • Epiphyseal and metaphyseal veins
  • Periosteal veins
• Femur transfers weight from hip to knee joint, causing tension on the lateral side of the shaft and compression on medial side