PHS 3504 - Chemical, Cellular, Tissue, and Organ Levels of Organization

• skeletal muscle tissue cells

  long, cylindrical, striated, multinucleate
• skeletal muscle

  - striated voluntary muscle

  
  

  - individual muscle cell is long, slender, having several hundred nuclei, called muscle fibers

  
  

  - skeletal muscle cells do not divide

  
  

  - new fibers are produced by divisions of myosatellite cells, a type of stem cells in adult skeletal muscle tissue
• types of muscle tissue

  1. Skeletal muscle - large muscles responsible for body movement

  2. Cardiac muscle - found in the heart

  3. Smooth muscle - found in walls of hollow, contracting organs
• muscle tissue

  specialized for contraction
• synovial membrane

  - line synovial joint cavities

  
  

  - synovial fluid produced for lubrication

  
  

  - lack a true epithelium
• cutaneous membrane


  - skin that covers that outer surface of the body

  
  

  - thick, relatively waterproof, and usually dry
• peritoneum

  lines peritoneal cavity and surrounds abdominal organs
• pericardium

  lines the pericardial cavity and surrounds the heart
• pleura


  lines the pleural cavities and covers the lungs
• serous membrane

  - line internal cavities of the body that do not open to the outside

  
  

  - line the pleural, pericardial, and peritoneal cavities

  
  

  - contains:

  - parietal layer - lines inner surface of cavity

  - visceral layer - covers the organ

  - serous fluid between the two layers - reduces friction
• mucous membrane

  - line passageways including digestive, respiratory, urinary, and reproductive tracts

  
  

  - epithelium covered by a layer of mucus secretion

  - to reduce friction

  - to facilitate absorption or secretion
• types of tissue membranes

  1. mucous membranes (mucosa)

  2. serous membranes (serosa)

  3. cutaneous membrane

  4. synovial membranes
• tissue membrane

  - line or cover body surfaces --> form physical barriers

  
  

  - consist of an epithelium supported by connective tissue
• ground substance in connective tissue proper

  - clear, colorless and viscous

  - contain various solutes

  - fills spaces between cells

  - slows pathogen movement
• Protein fibers in connective tissue proper

  - collagen fibers

  - reticular fibers

  - elastic fibers
• cells in connective tissue proper

  - Fibroblasts

  - Fibrocytes

  - Adipocytes

  - Mesenchymal cells

  - Melanocytes

  - Macrophages

  - Microphages

  - Mast cells

  - Lymphocytes
• types of connective tisse

  1. connective tissue proper - connect and protect

  2. fluid connective tissues - transport

  3. supporting connective tissues - structural strength
• basic components of connective tissue

  1. specialized cells

  2. extracellular protein fibers

  3. fluid (ground substance)
• connective tissue


  - a type of tissue with a diverse array of cells and other components

  
  

  - closely associated with epithelial tissue - connecting it to the rest of the body

  
  

  - never exposed to the outside environment

  
  

  - highly vascular

  
  

  - contain sensory receptors
• holocrine secretion

  - released by cells bursting

  - gland cells replaced by stem cells

  - ex: sebaceous glands

  
  

  - holocrine secretion occurs as superficial gland cells burst. Continued secretion involves the replacement of these cells through the mitotic divisions of underlying stem cells
• apocrine secretion

  - released by shedding cytoplasm

  - ex: mammary glands

  
  

  - apocrine secretion involves the loss of apical cytoplasm. Inclusions, secretory vesicles, and other cytoplasmic components are shed in the process. The gland cell then grows and repairs itself before it releases additional secretion
• merocrine secretion


  - released by secretory vesicles (exocytosis)

  - ex. merocrine sweat glands

  
  

  - in merocrine secretion, the product is released from secretory vesicles at the apical surface of the gland cell by exocytosis
• multicellular exocrine glands

  1. structure of the duct

  - simple (undivided)

  - compound (divided)

  2. shape of secretory portion of the gland

  - tubular (tube shaped)

  - alveolar or acinar (sack shaped/blind pockets)
• goblet cells


  unicellular glands in epithelia of intestines and respiratory tract, secrete mucin, which mixes with water to form mucus
• exocrine glands (unicellular and multicellular)

  - produce exocrine secretions

  
  

  - multicellular glands discharge secretions through ducts onto epithelial surfaces
• endocrine glands

  - release hormones into bloodstream

  
  

  - no ducts
• glands

  collections of epithelial cells that produce secretions

  
  

  structures that are attached to or derived from epithelia, produces fluid secretion
• pseudostratified ciliated columnar epithelium locations


  locations: lining of nasal cavity, trachea, and bronchi; portions of male reproductive tract

  
  

  functions: protection, secretion, move mucus with cilia
• simple columnar epithelium

  locations: lining of stomach, intestines, gallbladder, uterine tubes, and collecting ducts of kidneys

  
  

  functions: protection, secretion, absorption
• transitional epithelium

  locations: urinary bladder; renal pelvis; ureters

  
  

  functions: permits repeated cycles of stretching without damage
• simple cuboidal epithelium

  locations: glands, ducts, portions of kidney tubules, thyroid gland

  
  

  functions: limited protection, absorption, secretion
• stratified squamous epithelium

  locations: surface of skin, lining of mouth, throat, esophagus, rectum, anus, and vagina

  
  

  functions: provides physical protection against abrasion, pathogens, and chemical attack
• simple squamous epithelium

  locations: mesothelia lining pleural, pericardial, and peritoneal cavities; endothelia lining heart and blood vessels; portions of kidney tubules (thin sections of nephron loops); inner lining of cornea; alveoli of lungs

  
  

  functions: reduces friction; controls vessel permeability; performs absorption and secretion
• classification epithelia

  1. Based on shape

  • Squamous—thin and flat

  • Cuboidal—square shaped

  • Columnar—tall, slender rectangles

  2. Based on layers

  • Simple epithelium—single layer of cells

  • Stratified epithelium—several layers of cells

  
• desmosome

  - like buttons, they link neighboring cells to each other

  
  

  - help to stabilize cells and tissues and make them resistant to mechanical injuries
• tight junction

  - fusion of the cell membranes of two neighbor cells

  
  

  - prevent the diffusion of fluids/solutes between cells

  
  

  - "fluid-tight" seal

  
• gap junction

  - formed by interlocking transmembrane proteins (connexons) --> narrow passage

  
  

  - allow small molecules and ions to pass --> rapid communication

  
  

  - coordinate contractions in heart muscle and smooth muscle

  
• three types of cell junctions

  1. tight junctions

  2. desmosomes

  3. gap junctions

  
• cell junctions

  bonds between adjacent cells or extracellular material
• characteristics of epithelial tissue

  1. polarity (apical and basal/lateral surfaces)

  2. cellularity (cell junctions)

  3. attachment (basement membrane)

  4. avascularity (avascular, no blood supply)

  5. regeneration (stem cells)