Introduction and Epithelium Histology Introduction and Epithelium

HISTOLOGY HISTOLOGY: the study of tissues - the branch of anatomy that deals with the microscopic structure of tissues

HISTOLOGY tissues: groups of cells that are similar in structure & function

4 main types of tissue 1) Epithelial 2) Connective 3) Muscle 4) Nervous

All tissues are interconnected!

Epithelial Tissue

EPITHELIAL TISSUE Also known as EPITHELIUM Is the lining, covering, and glandular tissue of the body

FUNCTIONS OF EPITHELIUM Protection Absorption Filtration Secretion

Characteristics of Epithelium Cells fit closely together to form continuous sheets 2) Always one unattached (free) surface or edge * called the apical surface

Characteristics of Epithelium Lower surface of epithelial tissue rests on a basement membrane * thin layer of extracellular material to which epithelial cells are attached

Characteristics of Epithelium Epithelium is avascular = no blood supply of own  blood gets to these cells by diffusion from capillaries 5) Epithelial cells can regenerate easily (if well nourished)

Classification of Epithelium: Each type of epithelium has 2 names: First part of name = # of CELL LAYERS Second part of name = SHAPE

Classification of Epithelium: First name: Simple = one layer of cells, very thin Functions: absorption, secretion, filtration Stratified = two or more layers of cells, more durable Functions: protection

Classification of Epithelium: First name: Pseudostratified = “false” stratified, cells are different heights but still one layer

Classification of Epithelium: Second name: Squamous = flattened, like fish scales or floor tiles Cuboidal = cube-shaped, like dice Columnar = column-shaped, thinner

Classification of Epithelium: Simple vs. Stratified Stratified epithelia named for the cells at the free surface of the epithelial membrane

Simple Squamous Epithelium Single layer of flat cells resting on a basement membrane Location: lines air sacs of lungs, blood vessels, lines ventral body cavity Function: exchange of substances by rapid diffusion, filtration, secretion

Simple Squamous Epithelium

Simple Cuboidal Epithelium Single layer of cube-shaped cells resting on a basement membrane Location: salivary glands; kidney; ovaries Functions: Secretion and absorption

Simple Cuboidal Epithelium

Nonciliated Simple Columnar Epithelium Single layer of nonciliated rectangular cells resting on a basement membrane Location: lines digestive, respiratory, urinary tracts Function: Secretion and absorption

Nonciliated Simple Columnar Epithelium Contain absorptive and goblet cells Absorptive cells- columnar epithelial cells with microvilli (fingerlike projections that increase surface area, therefore increasing the rate of absorption) Goblet cells- modified columnar cells that secrete mucus Before mucus is released, it accumulates in the upper portion of the cell, causing that area to bulge out and resemble a goblet or wine glass

Simple Columnar Epithelium Epithelial membranes that line body cavities which open to the body exterior are called mucous membranes

Ciliated Simple Columnar Epithelium Single layer of ciliated columnar cells resting on a basement membrane Location: Upper respiratory tract Function: Moves mucus and other substances by ciliary action

Ciliated Simple Columnar Epithelium

Stratified Squamous Epithelium Multiple layers of cells, with squamous at the apical surface and cuboidal or columnar lining the basement membrane Location: Skin, mouth, throat Function: protection

Stratified Squamous Epithelium

Stratified Cuboidal Epithelium Two or more layers, with cube-shaped cells at the apical surface Location: large glands (sweat glands) Function: secretion

Stratified Cuboidal Epithelium

Stratified Columnar Epithelium Two or more layers of cells with columnar shaped cells at the apical surface Location: large glands Function: secretion

Stratified Columnar Epithelium

Transitional Epithelium Modified stratified squamous epithelium Basal layer: cuboidal/columnar Apical surface: vary in shape Location: urinary tract (bladder, ureters, urethra) Function: Cells can slide over each other to accommodate change in organ size Organs can stretch without rupturing

Transitional Epithelium

Pseudostratified Columnar Epithelium Single layer of ciliated columnar cells of varying heights resting on a basement membrane Location: lines respiratory tract Function: Secretion and movement of mucus by ciliary action

Pseudostratified Columnar Epithelium

1: simple squamous

2: simple cuboidal - kidney

3: simple columnar – small intestine

4: ciliated pseudostratified columnar - trachea

5. Stratified squamous epithelium – tongue

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Glandular Epithelium Function: secretion Glandular cells often lie in clusters deep to the covering and lining epithelium A gland may consist of one cell, or a group of highly specialized cells They secrete substances into ducts, onto a surface, or into the blood

Glandular Epithelium Endocrine glands Secretions enter extracellular fluid, then diffuse into the bloodstream without flowing through a duct Secretions are hormones (regulate metabolic and physiological activities to maintain homeostasis) Ex: pituitary, thyroid, adrenal glands

Glandular epithelium Exocrine glands Secrete into ducts that empty at the surface of covering/lining epithelium or directly onto a free surface Skin or interior space (lumen) of a hollow organ Secrete mucus, sweat, oil, earwax, milk, saliva, digestive enzymes Ex: sweat glands, salivary glands

Epithelium Review

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Histology What is a tissue?

Histology tissues: groups of cells that are similar in structure & function

Epithelial Tissue Is the lining, covering, and glandular tissue of the body

Functions of Epithelium Protection Absorption Filtration Secretion Pigeons Always Fly Straight

Characteristics of Epithelium Abut Apical surface Basement membrane Avascular Regenerate Another Awesome Byrne Anatomy Review! 

Characteristics of Epithelium Abut: Cells fit closely together to form continuous sheets 2) Apical Surface: Always one unattached (free) surface or edge

Characteristics of Epithelium Basement Membrane: Lower surface of epithelial tissue rests on * thin layer of extracellular material to which epithelial cells are attached

Characteristics of Epithelium Avascular: no blood supply of own  blood gets to these cells by diffusion from capillaries 5) Regenerate: Epithelial cells can regenerate easily (if well nourished)

Simple Squamous Specimen: artery Label: apical surface, nucleus of squamous cell

Simple Cuboidal Specimen: Kidney Label: cuboidal cell, nucleus

Simple Columnar Specimen: Small Intestine Label: goblet cells

Pseudostrified ciliated columnar Specimen: Trachea Label: apical surface, cilia

Stratified Squamous Specimen: Skin Label: squamous cell, apical surface

Transitional Specimen: Urinary bladder Label: apical surface