TISSUES

1
TISSUES

• Tissues - cells working together to perform a
  common function
• Histology - Study of tissues

2
4 BASIC TYPES

• Epithelial - covers lines surfaces, forms
  glands
• Connective - connects tissues, provides
  support, stores energy reserves
• Muscle - Contracts for movement, generates heat
• Neural - Carries information from one part of
  body to another in the form of electrical
  impulses

3
Epithelial Tissue - layer of cells that forms a
barrier

• Functions
• provides physical protection
• controls permeability
• provides sensations
• produces secretions
• Characteristics
• consists mainly of cells
• consists of single layer or multiple layers
• always has a free surface exposed to the
  environment
• avascular
• mitotic rate can be very high

4
Intercellular Connections

• Tight Junction - formed by fusion of cell
  membranes
• Desmosome - thin proteoglycan layer between
  opposing cell membranes
• Gap Junction - binding of membrane proteins

5
CLASSIFICATION Subdivided according to shape
arrangement of cells in each type

• Arrangements
• Simple - single layer of same shape
• Stratified - many layers of same shape
• Transitional - several layers of differing shapes

• Shapes
• Squamous - flat
• Cuboidal - cubed
• Columnar - higher than wide

http//trc.ucdavis.edu/biosci10v/bis10v/media/ch20
/epithelial_structure.html
6
SIMPLE SQUAMOUS(most delicate)

• Locations
• Alveoli in lungs
• blood lymphatic vessels
• Functions
• Reduce friction
• Diffusion of gases
• Controls permeability

7
STRATIFIED SQUAMOUS(tough)

• Locations
• Surface of skin
• Lining of mouth, throat, esophagus, rectum,
  vagina
• Functions
• Protection against abrasion, pathogens, and
  chemicals

8
SIMPLE CUBOIDAL

• Locations -
• glands, ducts, kidney tubules, thyroid gland
• Functions -
• protection, secretion, and/or absorption

9
STRATIFIED CUBOIDAL(RARE)

• Locations -
• lining of some ducts like sweat glands
• Functions -
• Protection, secretion, absorption

10
TRANSITIONAL EPITHELIUM(STRETCHY)

• Locations -
• Urinary bladder, ureters
• Functions -
• Permits expansion recoil after stretching

11
SIMPLE COLUMNAR

• Locations-
• Lining of stomach, intestine, gallbladder,
  uterine tubes, collecting ducts of kidneys
• Functions -
• Protection, secretion, absorption

12
PSEUDOSTRATIFIED COLUMNAR EPITHELIUM

• Locations -
• lining of nasal cavity, bronchi, trachea
• Functions -
• protection, secretion
• Nuclei are located at varying distances from
  surface

13
STRATIFIED COLUMNARRelatively Rare

• Locations -
• pharynx, epiglottis, anus, mammary ducts, urethra
• Functions -
• Protection

14
Glandular epithelium

• Cells that make up glands are specialized to
  produce and secrete substances
• Types of secretions from cells
• 1. endocrine
• Glands that secrete their products into tissues
  or blood
• Ex Pituitary and sex glands
• 2. exocrine
• Merocrine release products by exocytosis
• Ex salivary glands/ pancreas
• Apocrine Lose small portions of glandular bodies
  during secretion
• ex mammary glands fat droplets/sweat glands
• Holocrine entire cell disintegrates
• Ex sebaceous glands of skin (fatty mixture
  called sebum)