Glands Flashcards
How are the 2 main categories ided
According to the path of release of their secretions
Exocrine
Secrete into a system of ducts opening onto an epithelial surface
Endocrine glands
Release their product into the blood/lymph for transport to target tissues in another part of the body
Classification of exocrine
Unicellular
Multicellular - simple
Compound
Unicellular
Simplest In structure
Eg goblet cell of resp/ digestive tract
Goblet cell
Unicellular
Found in resp/digestive tract
Secretes mucin (a glycoprotein) which forms mucus on hydration
Don’t divide, terminally diff
Multicellular
Simplest form is epithelia where all/most cells are secretory eg surface epi of gastric mucosa
Simple multicellular glands
In branched duct system
May have branched secretory units
Compound multicellular gland
Larger gland
Branches duct system
More extensive secretory units
Simple types
Tubular Coiled tubular Branches tubular Acinar Branches acinar
Compound
Branches tubular
Acinar
Tubuloacinar
Mucus v mucous
Mucus is n
Mucous is adj
Simple tubular gland
Straight tube open directly onto epithelial surface
Minimal unbranched duct
Eg gland of intestinal mucosa, large intestine
Simple coiled tubular
Coiled secretory unit simple cuboidal epi lining
Unbranched duct stratified cuboidal epi lining
Eg sweat glands of skin
Simple branches tubular gland
Terminal secretory portion divided
Unbranched duct
Eg mucus secreting glands of pyloric region of stomach
Simple acinar gland
Occur as small pockets in epithelial surfaces
Eg Mucus secreting glands of penile urethra
Simple branched acinar
Several secretory acini empty into 1 unbranched duct
Eg sebaceous glands of skin
Eg if Holocrine secretion
Compound branched tubular gland
Branches tubular secretory units
Branched ducts
Eg duodenum (Brunner’s glands)
Compound acinar gland
Acinar secretory unit secrete into a branched duct system
Eg exocrine pancreas
Acini empty into minute duct at centre of acini cluster which empties into a branched excretory duct (simple cuboidal epi lined)
Compound Tubuloacinar gland
Combo of both secretory unit types
Eg mixed salivary glands like mandibular
Tubular secretory portion produce serous secretion
Acinar demo lines produce mucus secretion
Classify according to manner of discharge
Merocrine
Apocrine
Holocrine
Merocrine glands
Aka eccrine
Exocytosis
Secretory contents released through fusion of ltding mem of secretory vesicle with the cell mem
Most common form
Apocrine
Intact mem bound vesicles containing secretory product released
Uncommon, only applies to release of lipid secretions from mammary glands and some sweat glands
Holocrine glands
Release of secretory cells as a whole with subsequent disintegration of cells causing release of secretory products
Mainly in sebaceous glands
Describe due to type of secretion produced
Mucous
Serous
Sebaceous
Mucous secreting
Viscous colloid fluid rich in glycoproteins (mucus, antiseptic enz, immunoglobulin, inorganic salt, pros eg lactoferrin)
Mucous glands are part of mucous mem in resp/dig/urogenital tract.
Mucus key for protection and lubrication
Serous
Fluid rich in water and enz (protective or digestive enz) serous gland part of serous mem and production key for lubrication
Can make up part of distinct glands eg salivary
What makes up salivary gland
Serous portion for lube
Digestive enz
Sometimes buffering capacity through high level bicarbonate in secretions
Sebaceous
Oily, waxy sebum cont triglycerides, wax, squalene, free fatty acids
Found in the skin
Sebum helps waterproof skin & hair, has anti microbial properties
Eg of sebaceous secretion
Meibomian glands of eye lids produce lipid cogent of tears (w/out they wouldn’t be able to adhere to cornea to form tear film)
Ear wax also composed of sebum and other things
Where to find exocrine glands
Can form discrete glands, forming a definite mass appreciated grossly eg pancreas parotid liver
Can form diffuse glands through submucosa of the tissue eg poly stomatic sublingual salivary, sebaceous of the skin
Endocrine glands
Ductless
Secretory products diffuse directly into the CT of intercellular spaces from which it enters the blood stream
Product always hormone
Endocrine formation
Most develop in embryo from outgrowths/invagination a of epithelia lining cavities eg adrenal gland pituitary gland
Later lose their connections to the surface that they arose from
How endocrine secrete
Intimate and dense network of capillaries around cords or follicles of endocrine cells
Each clump of cells is also surrounded by a BM indicating epi origin
Follicular endocrine gland
Unusual as it stores hormone w/in spherical cavities enclosed by the cells of the gland
The cavities are called follicles and are found for eg in the thyroid
Glands
Groups of cells specialised for secretion
