epithelium Flashcards
Tissue
a group of cells that assemble to perform a common function
What are the four basic tissues in the body?
- Epithelium
- Connective tissue
- Nervous tissue
- Muscle tissue
Epithelium
-definition
Purely cellular
- a vascular layer or layers of cells covering all free surfaces of the body
- form glands of the body
- typicall one surface is free=face fluid or air
- other surface is attached to connective tissue
General Characteristics of Epithelium
- Highly Cellular
- No direct blood supply (avascular)
- Regeneration capacity
- Cells exhibit polarity
Apical Surface
- def
- function
- surface specialization
Free surface
-faces air or fluid
Function:
-absorption, recognition
Surface Specialization
- Cilia, microvilli, stereocilia
- clathrin coated vesicles
- Glycocalyx
Basal surface
- def
- function
- surface specialization
Attached surface
-usually connected to connective tissue
Function:
-attachment, transport, absorption
Cell Specialization:
- hemidesmosomes
- Membrane folds
Lateral Surface
- def
- function
- surface specialization
Attached to other epithelial cells
Function:
-attachment, communication
Surface Specialization:
- junctional complexes
- gap junctions
- Cell adhesion molecules (CAMs)
Types of Epithelium
-def
Lining or membranous epithelium
-covers the surface of the body and lines organs
Glandular epithelium
- forms glands (exocrine and endocrine)
- specialized for secretion
Functions of epithelia
- Protection
- Secretion
- Excretion
- Absorption
- Filtration
- Lubrication
- Reproduction
- Transport
- Sensory Perception
Histogenesis
epithelium is derived from all 3 germ layers
Microdomain
Region of cell membrane that has a distinct structure ofr function
What is the basement membrane composed of?
Basal Lamina
Reticular Lamina
Basal Lamina
Produced by epithelia
Two Parts:
- Lamina lucida
- Lamina Densida
Glycosaminoglycans
Collagen type IV-does not form fibrils
Laminin-glycoprotein, connects basal lamina to epithelial cells
Reticular Lamina
produced by connective tissue
-collagen III fibrils AKA reticular Collagen
Glycosaminoglycans (GAGs)
Functions;
- support
- Selective Filtration
Where is simple squamous found?
- Bowmans Capsule in kidney
- lines alveoli of lungs
Where are mesothelial cells found?
Mesothelium
- lines surface of body cavities
- Peritoneal, pleural, pericardial cavities
Where are Endothelium found?
lines blood vessels and lymphatic vessels
Where are Simple columnar cells found?
-Line the intestine
Funciton of simple columnar cells
absorption and secretion
Function of pseudo stratified columnar cells
absorption of material
Pseudostratified columnar
Can be:
Ciliated with Goblet Cells
- lines respiratory passages
- function in moving surface material
w/Stereocilia
- lines part of the male reproductive tract
- Long microvilli NOT CILIA
Stratified Squamous
-two types
- Cornified (AKA keratinized)
- contains filaggrin - Non-cornified (AKA nonkeratinized)
- keratin intermediate filaments present BUT NOT CROSSLINKED
Function of transitional epithelium
Accommodates stretch
-protects underlying tissue from hypertonic urine
Mucous Membranes
AKA mucosa
Mucous Secretion
-rich in proteins O-glycosylated with anionic oligosaccharides=more viscous thicker
-lines gastrointestinal and respiratory tracts
Function of mucous membranes
In GI Tract:
-viscous fluid (mucus) protects against chemical irritation)
In Respiratory Tract:
-traps inhaled particles
Goblet Cells
secrete mucus
Exocrine vs Endocrine
ALL EXOCRINE and MOST Endocrine glands are made of epithelia cells
2 endocrine exceptions
- Posterior Pituitary
- Adrenal Medulla
Exocrine
-products are secreted into ducts
Endocrine
- ductless
- produces hormones that are secreted into the bloodstream
- wrapped in capillaries
3 types of acini
- Acini
- Mucous
- Mixed (both serous and mucous)
- may or may not have serous demilune
Types of secretion
Serous Secretion (watery) Mucous Secretion (mucoid)
Serous Secretion
-general characteristics
Serous Acinus
-Watery
Pyramidal shaped cells -cell boundaries indistinct -spherical nucleus -Apical Secretory granules-stain acidophilic with H & E Basophilic cytoplasm around the nucleus
Secretory product
- proteinaceous
- thin, watery, and contains enzymes
Mucous Secretion
Mucous Acinus
-mucoid
Pyramidal shaped cells
- cell boundary distinct
- nucleus flattened an at base of cell
Secretory product (mucinogen)–thick an may act as a lubricant
- lost during preparation of the tissue=apical part of cell is clear with H&E
- only slight basophilia around nucleus
Mode of secretory product release
- Merocrine (eccrine)
- Aprocrine
- Holocrine
- Cytogenous
Mode of Secretory product: Merocrine
ECCRINE
- secretory granules fuse with cell membrane and contents ONLY are released
- serous or mucous
Mode of Secretory product: Apocrine
- secretion is released with plasma membrane enveloping the particle
- part of the cytoplasm leaves the cell
Mode of Secretory product: Holocrine
Whole cell dies and is secreted
Mode of Secretory product: Cytogenous
Whole living cell is released
Epithelia Cells
Cells with Epithelial characteristics but lack a free surface
