Epithelial Tissues

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Epithelial Tissues
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Tissues Introduction

• a group of similar cells specialized to carry on
  a particular function
• tissue cells extracellular matrix
• nonliving portion of a tissue that supports cells
• 4 types
• epithelial protection, secretion, absorption
• connective support soft body parts and bind
  structures together
• muscle movement
• nervous conducts impulses used to help control
  and coordinate body activities

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Epithelial Tissues Characteristics

• free surface open to the outside or an open
  internal space
• basement membrane anchors epithelium to
  underlying connective tissue
• lack blood vessels
• readily divide (ex. skin healing)
• tightly packed with little extracellular space

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Epithelial Classifications

• classified based on shape and of cell layers
• shape
• squamous thin, flat cells
• cuboidal cube-shaped cells
• columnar tall, elongated cells
• number
• simple single layer
• stratified 2 or more layers

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Epithelial Locations

• cover body surfaces, cover and line internal
  organs, and compose glands
• skin cells, cells that line the stomach and small
  intestine, inside of your mouth

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Simple squamous epithelium

• a single layer of thin, flattened cells
• look like a fried egg
• easily damaged
• common at sites of filtration, diffusion,
  osmosis cover surfaces
• air sacs of the lungs, walls of capillaries,
  linings of blood and lymph vessels

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Simple cuboidal epithelium

• single layer of cube-shaped cells
• centrally located nucleus
• secretion and absorption
• surface of ovaries, linings of kidney tubules,
  and linings of ducts of certain glands

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Simple columnar epithelium

• single layer of cells that are longer than they
  are wide
• nucleus located near basement mem.
• ciliated or nonciliated
• some have microvilli
• goblet cells secrete mucus
• absorption, secretion, protection
• linings of the uterus, stomach, and intestine

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Pseudostratified columnar epithelium

• appear stratified b/c nuclei are at 2 or more
  levels
• NOT stratified b/c all cells touch basement mem.
• ciliated
• goblet cells
• protection, secretion, movement of mucus
• linings of respiratory system

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Stratified squamous epithelium

• many layers of flattened cells
• named based on appearance of top layer of cells
• protection
• outer layers of skin, linings of oral cavity,
  throat, vagina, and anal canal

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Stratified cuboidal epithelium

• 2 or 3 layers of cuboidal cells
• protection
• linings of larger ducts of mammary glands, sweat
  glands, salivary glands, and pancreas

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Stratified columnar epithelium

• protection and secretion
• vas deferens, part of the male urethra, parts of
  the pharynx (throat)

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Transitional epithelium

• can stretch
• distensibility (stretching), protection
• inner lining of urinary bladder and linings of
  the ureters and part of urethra

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Glandular epithelium

• cells that are specialized to produce and secrete
  substances into ducts or into body fluids
• gland 1 or more cuboidal or columnar cell
• secretion
• salivary glands, sweat glands, endocrine glands

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Exocrine vs. Endocrine

• exocrine secrete sub. into ducts that open onto
  surfaces
• skin or linings of digestive tract
• endocrine secrete sub. into tissue fluid or
  blood
• hormones

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Exocrine glands

• merocrine release watery, protein-rich fluid by
  exocytosis
• salivary glands, sweat glands
• apocrine lose small portions of their cell body
  during secretion
• mammary glands, ear wax
• holocrine entire cell lysis (breaks apart)
  during secretion
• sebaceous glands of the skin

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Serous vs. Mucous

• serous typically watery with lots of enzymes
• lubrication
• mucous mucus
• digestive and respiratory systems
• protection