1.02 - Epithelium Flashcards
What is glandular epithelium?
Aggregates of cells, specialised to secret or excrete materials not related to their own metabolic needs
What are the two classifications of epithelium?
Simple (Single Layer)
Stratified (Two or more layers)
What are the types of Simple epithelium?
Squamous
Cuboidal
Columnar
Pseudostratified
What are the types of stratified epithelium?
Squamous
Cuboidal
Columnar
Transitional
Describe Simple Squamous Epithelium
Single layer of flat cells
Found at interfaces
Functions:
Diffusion - Lungs for gas exchange between air spaces and blood, Blood vessels for exchange of waste and nutrients between blood and surrounding tissue
Filtration - Kidney - plasma in glomeruli to produce urine
Secretion - lining of pleural, pericardial, peritoneal cavities (mesothelium), produces a lubricating substance to reduce friction
Describe Simple Cuboidal Epithelium
Single layer or square cells
Functions:
Absorption: Lining of ducts of kidney to move substances in and out of the kidney tubule.
Secretory: Lining of ducts of salivary glands and pancreas
Describe Simple Columnar Epithelia
Single layer of cells taller than they are wide (nucleus located towards the base) Can be ciliated or non-ciliated Functions: Absorption Secretion Protection
Describe Simple Columnar Ciliated Epithelium
Single layer of columnar cells with cilia
Cilia are short extensions of cytoplasm and cell membrane found on the free surface.
Involved in secretion of mucus and other substances and in moving luminal contents, e.g. fallopian tubes and bronchi.
Describe Simple Columnar Epithelium with Microvilli
Single Layer of Columnar cells with Microvilli.
Microvilli are closely bunched tiny projections from the free surface of cells.
Core of actin filaments.
Can have a layer of Glycocalyx on the free surface.
Function:
Absorption: Small & Large Bowel (glycocalyx located here)
Secretion: Stomach and Uterus - Secretion of mucus, enzymes and other substances
What is glycocalyx?
An extracellular polymeric material made up of lipids, proteins with carbohydrate side chains and contains within it enzymes for digestion
Describe Simple Columnar Epithelium with Goblet Cells
Single layer of Columnar cells with Goblet Cells
They are modified columnar cells that synthesise and secrete mucous
At the apex of the cell are mucigen granules with the nucleus and other organelles located at the base
Function:
Secretion - Small and large intestine
Describe Pseudostratified Ciliated Columnar Epithelium
A single layer of cells that appear as two or more layers
All cells rest on basement membrane but nuclei are on different levels
Function: Secretion, Lubrication, Protection, Transportation
Location: Respiratory epithelium of bronchus
Describe Stratified Squamous Epithelium
2 or more layers of squamous cells
Function: Mainly protection - resist abrasion
Transition from cuboidal basal layer to flattened surface layer
Can be keratinising or non-keratinising
What is Keratin and what is it’s function?
It is a tough protective protein which prevents water loss, is resistant to friction and repels bacteria.
Where can Keratinised and Non-Keratinised Stratified Squamous Epithelium be found?
Keratinised: Epidermis of the skin, masticatory mucosa
Non-keratinised: Lines surfaces subjected to abrasion - lining of the mouth, oesophagus, tongue and vagina
What are desmosomes and where are they found?
A type of intercellular junction that are characterised as dense regions of attachment between epithelial cells that contribute to strong bonds between cells
Found between squamous epithelium
Describe Stratified Cuboidal Epithelium
2 or 3 layers of cuboidal cells
Robust lining
Not much absorption or secretion
Found in the larger ducts of exocrine glands, such as salivary and sweat glands.
Describe Stratified Columnar Epithelium
Several layers of epithelial cells but surface layer is made of columnar cells
Roles are protection and secretion
Only located in part of the male urethra, portion of the conjunctiva
Describe Stratified Transitional Epithlium
Stratified epithelium
Intermediate between stratified cuboidal and stratified squamous
4 or 5 cells layers
Basal cells are cuboidal, surface large and rounded
Function: Protective and Distensible
Location: Bladder - stretch and copes with toxicity of urine
What are the three types of glands?
Goblet cells (unicellular) Exocrine (Multicellular) - release their products on to free surface of skin or open cavities of body - e.g. sweat and salivary glands Endocrine (multicellular) - their product (called hormones) are secreted directly in to the blood - e.g. islet cells of pancreas
What are the functions of Epithelium?
Diffusion - alveoli of lungs
Barrier - skin
Containment - endothelium - blood brain barrier
Excretion - Collecting ducts of kidney
Secretion - breast (milk), skin (sweat), GIT (mucous), pancreas (hormones)
Absorption - small intestine
Contractility - bladder, salivary glands
Sensation - taste buds, olfactory epithelium
