Lecture 1 Flashcards
Tissue:
a group of similar cells that are specialized toperform a common function”.
* Cells have particular arrangements
* Cells have particular size of aggregation
* Cells have particular shape
* Cells are surrounded by extracellular matric (ECM)
Histology
“the biology of tissues
ORGANIZATION IN HUMAN BODY
cell
tissue
organ
organ system
organism
four basic types of tissue
epithilium
connective
muscle
nervous
Epithelial tissue
Derived from the three germ layers: endoderm, mesoderm
and ectoderm.
* Forms glands (exocrine and endocrine glands).
* Lines the inside and outside of organs and body cavities.
* Covers the body externally (i.e. skin).
GENERALIZATIONS in epithelial
Adjacent cells are attached to each other.
* Apical and Basal surfaces.
* Attaches to underlying connective tissue by means of basement membrane.
* No ECM…Avascular no blood cells
* Undergo mitosis regularly
BASEMENT MEMBRANE
Thin, non-cellular layer of adhesive, permeable material
FUNCTIONS OF EPITHELIAL TISSUE
Protection
* Membranous epithelium - skin
Sensory
* Ears, eyes, nose, skin
Secretion
* Glandular epithelium
Absorption
* Intestinal and respiratory
Excretion
* Kidney tubules
Surface epithelium - epithelial tissue type
Forms continuous sheets with one or more layers of cells.
* Epithelial cells lie on a basement membrane.
* Presence of surface specializations (if any).
epithelial tissue type Glandular epithelium
Invaginations of the surface epithelial tissues to form glands that
are involved in secretion and excretion of substances.
* Ductless glands.
* Subdivided as: Exocrine glands or Endocrine glands.
how are epithelial tissue classified
number of cells
shape of cells
presence if any of surface specializations
number
-simple, stratified or pseudostratified**
shape
-squamous, cubodial, columar
surface specializations
-keratin, microvilli, cilia, stereocilia** (only in male reproductive system)
SIMPLE SQUAMOUS
One layer of cells = Simple
* Flat, irregular shaped cells = Squamous
Function:
* Thinnest epithelium for diffusion, infiltration and lubrication.
* Location:
* Lining of the blood vessels, lining of renal corpuscles, lining of internal body cavities, alveoli of the lungs
Peritoneum, vascular endothelium, mesothelium, alveoli of the lungs, Bowman’s capsule, loop of Henle of
the kidneys
SIMPLE CUBOIDAL EPITHELIUM
- One layer of cells = Simple
- Square, shaped cells = Cuboidal
Function: - Absorption, secretion and excretion.
- Location:
- Lining of small ducts and tubules that have absorptive, secretory or excretory functions (e.g., collecting tubules of the kidney, small ducts of the salivary glands and pancreas)
if they have microvilli on them they are found Proximal convoluted tubules of the kidney
SIMPLE COLUMNAR EPITHELIUM
- One layer of cells = Simple
- Tall, thin shaped cells = Columnar
- Variable height depending on the site of activity.
- Nuclei – apical, medial, basal location; polarity of the nucleus
- Function:
- Lining of gastrointestinal tract and absorption.
- Location:
- GI tract (stomach to anus), glands, uterus, Gallbladder, stomach,endocervix
if they have Microvilli + goblet cells =Small intestine, large intestines
if they have Cilia = Fallopian tube
if they have Pseudostratified with cilia +
goblet cells =Respiratory tract, nose, sinuses
if they have Stereocilia = Vas deferens
STRATIFIED SQUAMOUS EPITHELIUM
- More than one layer of cells = Stratified
- Only the basal cell is anchored to the basement membrane.
- Flat, irregular shaped cells on the apical surface = Squamous
- Basal cells are cuboidal → polygonal → squamous
- Function:
- Protect underlying tissue from mechanical abrasion.
- Location:
- Lining of the skin epidermis (SSK)
- Lining of oral cavity, esophagus and vagina (SSNK) cornea
KERATIN
Protein; found in epidermis, finger nails and hair.
* Surface specialization only found in stratified squamous
epithelium of the skin epidermis.
* Helps to protect water and prevent water loss.
* During maturation, epithelial cells accumulate cytokeratin
and undergo keratinization resulting in formation of tough,
non-living surface of keratin.
* Keratinizing – sloughing off of dead keratin, aka. squames.
STRATIFIED SQUAMOUS KERATINIZING
Dry type of epithelium.
* Stratification – protection.
* Keratin – prevent water loss.
* The epithelium is covered with keratin.
* The topmost layer is formed of squamous cells that are keratinized and dead. no nuclei
* Flattened non-nucleated cells on apical surface
* Location:
* Only found in the skin epidermis
STRATIFIED SQUAMOUS NON-KERATINIZING
(SSNK)
Wet type of epithelium – water loss not a concern.
* Stratification – protection.
* The topmost layer is formed of squamous cells.
* The epithelium is not covered with keratin.
* Flattened nucleated cells on apical surface.
Location:
* Lining of oral cavity, esophagus and vagina
STRATIFIED CUBOIDAL EPITHELIUM
More than one layer of cells = Stratified
* square shaped cells = Cuboidal
Function:
* Strengthen and support for the “walls” of the ducts.
* Location:
* Large excretory ducts of exocrine glands
STRATIFIED COLUMNAR EPITHELIUM
More than one layer of cells = Stratified
* Tall, thin shaped cells = Columnar
* Cells at the basal layer are cuboidal in shape and cells at the apical (top) layer are columnar
Function:
* Strengthen and support for the “walls” of the ducts.
* Location:
* Largest ducts of the body
TRANSITIONAL EPITHELIUM
Also known as: Urinary epithelium.
* More than one layer of epithelial cells.
* Apical layer: Dome-shaped, umbrella shaped
Function:
* Protection, stretching and distension.
* Location:
* Urinary system: ureter, urinary bladder, prostatic urethra
MICROVILLI
Non-motile, finger-like projections
* Brush border appearance (a little border on top of the cells that isnt a keratinaized layer kinda border)
Function:
* Increase the surface area for absorption (at least 30x fold).
* Location:
* Gastrointestinal tract (GIT)
CILIA
Motile, finger-like projections
Function:
* Motility: moves and propels and moves fluid or minute particles across the apical surface of the cell.
* Location:
* Female reproductive system and respiratory tract
they look like swept brushes to the side
STEREOCILIA
Long, non-motile, microvilli
Function:
* Absorption: removes excess testicular fluid and provides nutrients
to sperm cells.
* Location:
* Unique to the male reproductive system.
GOBLET CELLS
Specialized type of epithelial cell – unicellular gland
Function:
* Produces and secretes mucous.
* Location:
* Respiratory tract and Gastrointestinal tract (GIT)
Functions of mucous:
* Protects upper intestinal lining from autodigestion.
* Lubricates the passage of feces in the colon.
* Protects lining of the respiratory tract from drying.
* Contributes to dehumidification of inspired air.
* Traps fine dust particles.
PSEUDOSTRATIFIED COLUMNAR
- Variation of simple columnar epithelium.
- One layer of cell = Simple
- Different heights but each cell is attached to the basement membrane.
- Tall, thin shaped cells = Columnar
- PSEUDO = false, STRATIFIED = multiple layers
- “Falsely stratified” columnar epithelium
PSEUDOSTRATIFIED COLUMNAR
WITH GOBLET CELLS AND CILIA
AKA. Respiratory epithelium
* One layer of cells but looks stratified = Pseudostratified
* Thin shaped cells = Columnar
* Specialized cells = Goblet cells
* Surface specialization = Cilia
* Function
* Secretion and propulsion.
* Location:
* Lining the respiratory tract.
SIMPLE COLUMNAR
WITH GOBLET CELLS AND MICROVILLI
One layer of cells = Simple
* Tall, thin shaped cells = Columnar
* Specialized cells = Goblet cells
* Surface specialization = Microvilli
* Location:
* Small and large intestine
