Chapter 5
Endocrine & Exocrine
Glands
Endocrine and Exocrine Glands
•
gland – cell or organ that secrete substances for use elsewhere in
the body or releases them for elimination from the body
–
•
exocrine glands - maintain their contact with the body surface by
way of a duct (epithelial tube that conveys secretion to surface)
–
•
hormones – secretion of endocrine glands
secrete (hormones) directly into blood
thyroid, adrenal and pituitary glands
some organs have both endocrine and exocrine function
–
•
sweat, mammary and tear glands
endocrine glands - lose their contact with the surface and have no
ducts
–
–
–
•
composed of epithelial tissue in a connective tissue framework and
capsule
liver, gonads, pancreas
unicellular glands – found in epithelium that is predominantly
nonsecretory
–
–
can be endocrine or exocrine
mucus-secreting goblet or endocrine cells of stomach and small intestine
Exocrine Gland Structure
Lobules
Secretory
acini
Lobes
Duct
Parenchyma
Secretory
vesicles
Stroma:
Capsule
Septum
(a)
Duct
Acinus
(b)
•
capsule – connective covering of most glands
–
–
•
stroma – connective tissue framework of the gland
–
•
septa or trabeculae – extensions of capsule that divide the interior of the gland into
compartments (lobes)
further divided into smaller lobules
supports and organizes glandular tissue
parenchyma – the cells that perform the tasks of synthesis and secretion
–
typically cuboidal or simple columnar epithelium
Structural Types of Exocrine Glands
Simple coiled tubular
Compound acinar
Compound tubuloacinar
Example: Sweat gland
Example: Pancreas
Key
Example: Mammary gland
Duct
Secretory portion
•
•
•
simple - unbranched duct
compound - branched duct
shape of gland
–
–
–
tubular – duct and secretory portion have uniform diameter
acinar - secretory cells form dilated sac (acinus or alveolus)
tubuloacinar - both tubular and acinar portions
Types of Secretions
•
serous glands
– produce thin, watery secretions
• perspiration, milk, tears and digestive juices
•
mucous glands
– produce glycoprotein, mucin, that absorbs
water to form a sticky secretion called mucus
– goblet cells – unicellular mucous glands
•
mixed glands
– contain both cell types and produce a mixture
of the two types of secretions
•
cytogenic glands
– release whole cells, sperm and egg cells
Methods of Secretion
The Merocrine Glands
•
merocrine glands (eccrine
glands) – have vesicles that
release their secretion by
exocytosis
– tear glands, pancreas, gastric
glands, and others
•
Exocytosis
Nucleus
Secretory
vesicle
Merocrine gland
apocrine glands – primarily
merocrine mode of secretion
– axillary sweat glands,
mammary glands
Methods of Secretion
The Holocrine Glands
Holocrine gland
•
Cells accumulate a product and then the entire cell disintegrates
– secretion a mixture of cell fragments and synthesized substance
– oil glands of scalp, glands of eyelids