Lecture 8: Glandular Epithelia Learning Objectives
-understand the difference between exocrine and endocrine glands
-identify glandular epithelia and give examples
BASIC TISSUE TYPES
Epithelial tissue: covers body & organ surfaces, lines body
cavities, forms glands.
Connective tissue: binds, supports and protects body structures,
stores energy and minerals
*Nervous tissue: initiates and transmits nerve impulses to
coordinate physiological function
*Muscle tissue: contracts and relaxes to produce movement
*Excitable tissues
Goblet cells Epithelial cells that synthesise and secrete
mucus also known as unicellular exocrine
glands
Goblet cells are modified columnar epithelial
cells that synthesise and secrete mucus
Scattered among cells of many simple
epithelia, especially respiratory & GI tracts
Apical cytoplasm contains mucigen granules
Mucigen is composed of neutral and acidic
proteoglycans called mucopolysaccharides
Lining of small intestine
Goblet cell PAS / haematoxylin ×800
PAS stains carbohydrate magenta
Goblet cells A –Absorptive cells
N –Nucleus
rER–rough endoplasmic
reticulum
M –Mitochondria
G –Golgi apparatus
Mu –mucigen
Mv–microvilli
BB –Brush border
Goblet cell EM ×5000
Exocrine glands Exocrine glands: discharge secretory product via a duct onto an epithelial surface
Composed of highly specialised epithelial cells
Invaginations of epithelium surfaces which discharge secretory product
Continuous basal rate of secretion, modulated by nervous and hormonal influences
Exocrine glands can be divided into the secretory component and the duct.
The duct system may be branched (compound gland) or unbranched (simple gland)
Vary from microscopic (eg sweat glands of the skin) to large solid organs (eg. Liver)
Secretory component may be tubular or acinar (roughly spherical).
Secretory component may also be coiled or branched
Secretory Methods Merocrine
Apocrine
Holocrine
Direct exocytosis of protein
Discharge of membranebound vesicle
Discharge of cells,
disintegrating to release
product
Most common (eg.
pancreatic enzymes)
Uncommon (eg. Lipid
secretions in mammary
glands)
Sebaceous glands
Simple tubular A single, straight tubular lumen into
which the secretory products are
discharged eg. mucus-secreting gland
of the colon
Large intestine
H&E x 50
Simple coiled tubular A single tube, tightly coiled in 3
dimensions eg. Sweat glands (almost
only example)
Sweat gland
H&E x 80
S –Terminal secretory portion
D –duct (non-secretory)
Simple branched tubular Several tubular secretory portions (T)
converge onto a single unbranched
duct (D) eg. Mucus-secreting gland of
the stomach
Pyloric region of stomach
H&E x 60
T –Tubular secretory portion
D – duct
Simple Acinar Occur in the form of pockets in
epithelial surfaces. Lined by secretory
cells eg. penile urethra
H&E x 120
U - urethra
Simple Branched Acinar Each gland consists of several
secretory acini (A) that empty into a
single excretory Duct eg. Sebaceous
glands, sebum secretion (holocrine)
Masson’s trichome x 80
A – acini
E – excretory duct
Compound Branched Tubular Secretory portion is branched and
coiled and the duct system is also
Branched (difficult to visualise) eg.
Brunner’s gland of the duodenum
H&E x 20
S – secretory portion
D –duct
Compound Acinar Secretory units are acinar and drain
into a branched duct system eg.
pancreas
Pancreas
Chrome alum haematoxylin/phloxine x 320
E – excretory ducts
D – minute ducts
Compound Tubulo-­‐Acinar E – Excretory ducts
D – Demilunes
T – Tubular components
A – Acinar components
3 types of secretory units:
branched tubular, branched acinar and branched
tubular with acinar end-pieces called demilunes
eg. Submandibular salivary gland
Submandibular salivary
gland
H&E x 200
Endocrine glands Endocrine glands have no duct system but can release their secretions directly into
the bloodstream
Endocrine glands are the source of many of the body's chemical messengers,
hormones that act at a distance from their source eg. insulin
In general secretion of hormones by endocrine glands is controlled by
metabolic factors (e.g. blood glucose levels)
secretion of other hormones (e.g. TSH controls secretion of thyroxine)
the nervous system (e.g. the secretion of adrenaline by the adrenal medulla)
or a mixture of all of these factors.
Endocrine system is one of the 2 major regulators of physiological function (along
with the nervous system
Endocrine glands Clumps of secretory cells surrounded by a
basement membrane; further surrounded by
capillary network
Pituitary gland
Isamine blue eosin x 128
S –Secretory cells
C –capillaries
Secretory cells are of varying types
and hence stain differently
Endocrine glands Hormone stored within follicles (spheroidal
cavities enclosed by secretory cells)
Before release, hormone is reabsorbed,
released into interstitium and thence into
capillaries
Thyroid gland
H&E x 150
F – Follicles
C –capillaries
Secretory cells are flattened cuboidal
Stored TH bound to a strongly
eosinophilic glycoprotein (hence pink)