Show Menu
Cheatography
  1. Home >
  2. Education >

VETS1022 Mr.Nha Histology Cheat Sheet (DRAFT) by

Mr. Nha histology subject

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Epithelial Tissue

Introd­uction:
- Covering
- Glandular
Covering (Biểu mô phủ):
- Covers exposed surfaces
- Lines internal tracts (of digestive/ respir­atory/ urogen­ital)
- Line cavities (thorax, abdomen, heart,...)
Glandular:
Forms 2 types of gland:
- Exocrine
- Endocrine
Eoxocrine glands line under the epithelial layer, above the connective tissue layer, lie across different sections of the body

Charac­ter­istics of epithelia

Cellul­arity
Cells bound together by various types of cell junctions (gap junctions, tight junctions)
Polarity
Apical surface:
- Pointing towards the external enviro­nment or internal space
- Specia­lis­ations: cillia, microv­illi, stereo­cillia
Basal surface:
- Attached to the basal membrane (Basale lamina)
- Surfaces differ in structure and function
Attachment :
Basal surface attached to a basement membrane made of a thin layer of mucopo­lys­acc­harides and proteins
Avascu­larity:
- Dont contain blood vessels
- Obtain nutrients by diffusion or absorption
Regene­ration:
- High rate of cell division (mitotic index)
- Damaged or dead cells at the exposed surfaces are replaced with basal stem cells goin up

Roles of Epithelia

Protection:
Against abrasion, dehydr­ation, damage from chemical or biological agents
Permea­bility:
Any substance has to cross a layer of epithelium ( via diffusion, pumps, channels)
Sensation:
- Innervated by sensory nerves
- Specia­lised epithelial cells can detect changes in enviro­nment and convey info to nervous system
Secretion:
Gland cells: secrete fluids
 

Classi­fic­ation (BASED ON ARRANG­EMENT)

Simple: one cell layer
- Simple squamous (flattened)
- Simple cuboidal (width approx. height)
- Simple columnar ( height > width)
Stratified: multiple layers
- Stratified squamous
- Stratified cuboidal
- Stratified columnar
Pseudo­str­atified Columnar:
- Tall principle cells and short pyramidal basal cells
- ALL cells rest on basement membrane but NOT ALL reach the Lumen.
Transi­tional:
Special type of Stratified that can stretch and made up different types of epithelial cells

Types of Simple

Simple Squamous:
- Flattened, polyhedral cells with a bulging nucleus
- Delicate, found in protected regions (away from external enviro­nment)
- Allows for easy exchange of gases, ions and small molecules
- Lines lung alveoli, body cavities, heart, blood vessels
Simple Cuboidal:
- Cuboidal in longit­udinal section, Polygonal in cross section with a central nucleus
- Involved in: secretion, absorp­tion, excretion
- Found in : glands, ducts, parts of kidney tubules, thyroid gland
Simple Columnar:
Height > width with basal nucleus usu. same level across
- Involved in: Protec­tion, absorp­tion, secretion (have microvilli and cillia)
- Lining of stomach, intest­ines, oviducts, collecting ducts of kidneys
- Often have modified apical surface (micro­vil­lia­/ci­llia)

Pseudo­str­atified Columnar

- Tall principle cells and short pyramidal basal cells
- All cells stems from BASAL LAMINA but not all reach the LUMEN
Found in: nasal cavities, trachea, bronchi
--> Have cillia; propel mucous and trapped particles to the pharynx
- Also found in Epididymis (stere­oci­llia)

Stratified Squamous

Stratified Squamous:
- Found in: places needed mechan­ica­l/p­hysical protec­tion: skin, linings of mouth, esophagus and anus
- Protects against: abrasion, pathogens, chemic­al/­bio­logical agents
- Regene­ration: Basal cells multiply --> move towards surface --> flattening and degene­rating as they reach superf­icial layers
- Classified into: Kerati­nised and Non-ke­rat­inised
Non - kerati­nised: in mouth, keep moist by glandular secretions
Kerati­nised: In places with mechanical and dehydr­ation problems; keratin deposited in cells as they mature --> harden, form tough, acellular surface layer as they die
Four Major Strata:
- Stratum corneum Cornified layer (dead kerati­nised cells)
- Stratum granulosum: Granular layer ( keratin and granules forming)
- Stratum sphosum: "­Prickle cell" layer (many desmosomes)
Stratum germin­ativum: Germinal layer (forming new cells)
NOTE:
- Basal cells divide contin­ously --> Daughter cells push upwards --> Mature then degenerate --> Are shredded
- Basal cells are cuboidal --> become squamous as moving upwards --> Lose nucleus as peak maturity
  

Stratified Cuboidal and Columnar

Stratified Cuboidal
Structure:
- 2 to 3 layers of cuboidal or low columnar --> more robust lining than its simple counte­rpart
- Rare, found in: ducts of salivary, sweat, mammary glands
Stratified Columnar
Structure:
- Basal layer: cuboidal
- Apical layer: columnar
Rare, found in: Urethra, ducts of salivary glands

Trasit­ional

Charac­ter­istics:
- Stratified
- Various cell shapes:
+ Basal cells: cuboidal
+ Interm­ediate: polygonal
+ Apical: round and sometimes binucleate
- Accomm­odates to toxicity of urine
- High degree of stretch
- Only in urinary tracts

Functional Correlates

Know types of epithelial cells --> Functions of an organ
Ex:
- Simple usu. means absorp­tion, secretion
- Strati­fied: robust protection
--> Stratified Squamous: protection of places subjected to wear and tear
--> Simple cuboidal: secretion of glandular fluids
--> Columnar with microv­illi: absorption