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