TOB S2 - Glands and Internal surfaces of the body Flashcards
Define a gland.
A collection of epithelial cells specialised for secretion.
List the ways in which glands are classified.
Destination of secretion
Structure of gland
Nature of secretion
Method of discharge
How are glands classified by secretion destination?
Exocrine glands secrete into ducts or onto surfaces
Endocrine glands are ductless, secrete directly into blood
How are the secretory portion of glands classified by structure?
Uni/multicellular
How are multicellular glands classified? (think shape of secretory portion)
Alveolar, tubular, coiled, branched
What are the different types of ducts present in glands?
Simple
Complex (branched)
How are glands classified by nature of secretion?
Mucous or serous
Describe mucous secretion.
How does it react to H&E staining?
Contains mucus rich in mucin (glcosylated polypeptides)
Stains poorly with H&E stain
Describe serous secretions
How does it react to H&E staining?
Watery, no mucus, enzymes present
Stains pink with H&E stain
What are the three methods of secretion?
Merocrine, Apocrine, Holocrine
Describe the process of merocrine secretion
Membrane bound vesicle fuses with plasma membrane
Contents released into intracellular space
Additional area of plasma membrane recovered
Describe the process of Holocrine secretion.
Disintegration of whole cell releases all cellular contents
Describe the process of Apocrine secretion
Non membrane bound structures (eg. Lipids) approach apical cell membrane, are enveloped by cytoplasm then the plasma membrane.
Buds off releasing vesicles into intercellular space
Large amounts of plasma membrane lost (decapitation)
Plasma membrane added to to recoup loss.
What is endocytosis?
The opposite process to exocytosis (merocrine secretion)
Material outside cell is engulfed by plasma membrane and buds off into the cell cytoplasm.
Describe transepithelial transport
Material enters cell through endocytosis
Shuttled through cytoplasm in transport vesicle
Material is secreted on the other side of epithelial cell via merocrine secretion (exocytosis)
Describe the structure of the Golgi apparatus
Layers of disk shaped cisternae
Flattened on one side, concave on the other
Swellings at the edges of cisternae (bud off to form vesicles)
Describe the functions of the Golgi apparatus
Sorting and packaging of contents into vesicles
Glycosylation of proteins and lipids
Transport
Where do vesicles from the Golgi apparatus end up?
Majority exocytosed
Some retained (eg lysosomes)
Some enter plasma membrane (glycocalyx)
Why is the Golgi apparatus important to the maintenance of the glycocalyx?
Complex branching sugars produced in Golgi apparatus important to specific interactions of the glycocalyx.
How does enzyme damage to the glycocalyx affect its function?
Alters specificity based interactions of glycocalyx such as:
Adhesion to substrates and other cells
Communication with adjacent cells
Cell mobility
Contact inhibition of movement or division
What are the simple mechanisms of control of secretion?
Nervous control
Endocrine control
Neuro-endocrine control
Negative feedback chemical mechanism.
Give an example of nervous control of secretion
Sympathetic nervous stimulation of adrenal medullary cells promotes release of adrenalin.
Give an example of endocrine control of secretion
Adrenocorticotrophic hormone stimulates the cortex of the of the adrenal gland to release hormones (eg cortisol)
Give an example of neuro-endocrine control.
Nervous cells of the hypothalamus control ACTH secretion from the anterior pituitary gland
Give an example of negative feedback chemical mechanism
Inhibitory effect of high thyroxine levels on TSH synthesis in the anterior pituitary gland.
Mucous membrane line what kind of surface?
Give examples
Surfaces that open to the exterior
Alimentary tract
Respiratory tract
Urinary tract
What are the constituents of a mucous membrane (ordered from apical descending)?
Epithelium
Adjacent layer of connective tissue (lamina propria)
Smooth muscle layer (muscularis mucosae)
In addition variable amounts of mucus secreting cells.
Describe a serous membrane and where are they found? Give examples.
Thin two part membranes found lining viscera (interior surfaces that don’t open to exterior)
Pleural sac
Peritoneal sac
Pericardial sac
What is the function of a serous membrane?
Secrete a lubricating fluid which promotes relatively friction free movement of the organs they surround.
What are the layers of a serous membrane and each layers function?
Simple squamous epithelium - secretes lubricating fluid
Connective tissue layer - attaches epithelium to adjacent tissues and carries nerves and blood vessels, contains lymphocytes
During embryonic development, how does a serous membrane come to surround an organ/s?
Heart lungs and gut develop next to a bag like cavity (serosa) into which they invaginate, hence becoming surrounded by the two layers of the serosa.
What are the layers of the alimentary tract?
Mucosa Muscularis mucosa Sub mucosa Muscularis externae Serosa
What is the function of the Muscularis externae in the alimentary tract?
Creates peristaltic waves to move luminal contents along
Between what layer of the alimentary tract is the mesentary found?
Between the serous epithelium and connective tissue.
In the abdomen what determines whether an organ is covered by serosa or adventitia?
Peritoneal organ - serosa
Retroperitoneal - adventitia
What are the stomach rugae?
Folds in the gastric mucosa forming longitudinal ridges in an empty stomach
What is secreted by the gastric mucosa?
Acid, gastric enzymes, gastrin (hormone)
How many layers does the gastric muscularis externa have?
3
Oblique, circular, longitudinal
What are the pilicae circulares of the jejunum?
Circular folds of mucosa and submucosa that project into the lumen
What are the layers of the trachea?
(Respiratory) Mucosa
Submucosa
Fibroelastic membrane with trachealis muscle and C-shaped hyaline cartilage
Adventitia
What is the function of the epithelium in the colon?
Epithelial cells in the crypts supply mucus and cells to surface
Surface epithelia absorb water and electrolytes.
What section of the respiratory system is the conducting portion and what section is the respiratory portion?
Conducting: Trachea to bronchioles
Respiratory: bronchioles to alveoli
What are the layers of the bronchi?
Mucosa
Smooth muscle
Submucosa - contains glands
Crescent shaped cartilage (smaller than in trachea)
What are the layers of the bronchioles?
Epithelia
Smooth muscle
What glands are present in the mucosa of the trachea?
Sero-mucus glands (decreasing closer to bronchioles)
What is the function of the c shaped hyaline cartilage?
Prevents tracheal collapse
What types of epithelia are found in bronchioles?
Larger bronchioles: simple columnar ciliates
Smaller bronchioles : simple columnar non ciliates
Small sacs extending from wall of terminal bronchioles: simple cuboidal
Alveoli are how many cells thick?
1 cell thick
What types of cells are found in alveoli?
Type 1 = squamous (90%)
Type 2 = cuboidal (10%)
Macrophages
What are the functions of cells of the alveoli?
Squamous epithelia permit gas exchange
Cuboidal epithelia produce surfactant
Macrophages phagocytose inhaled particles.
What are the layers of the ureter?
Epithelium
Lamina propria - fibroelastic
Muscularis externa - circular
What are the layers of the bladder wall?
Epithelium Smooth muscle (in the lamina propria) Muscularis externa (3 interwoven layers)
Why is the epithelia of the bladder wall impermeable to urine?
Thick plasma membrane and intercellular tight junctions
What are the tissue layers of the urethra?
Epithelium
Lamina propria
Muscularis externa - circular and longitudinal
Adventitia
What type of epithelia is found in the urethra and what different type is found in the penile section of the urethra?
Transitional
Stratified columnar
Give a list of all types of simple and complex glands.
Simple:
Tubular, alveolar, coiled, branched tubular, branched alveolar
Complex:
Tubular, alveolar, tubuloalveolar
