Lesson 2: Glandular Epithelia/ Exocrine glands Flashcards
What is the primary function of glandular epithelia?
To produce and release secretions via exocytosis, including precious products, not metabolic wastes.
What are the two types of glandular epithelia?
Exocrine glands (secretion via ducts) and endocrine glands (secretion into the bloodstream).
What are the six principles of exocrine gland classification?
Number of cells, site, shape of the terminal secretory unit, branching of ducts, mode of secretion, and nature of secretion.
What is an example of a unicellular exocrine gland?
Goblet cells - columnar epithelial cells
Where are goblet cells commonly found?
Respiratory tract, gastrointestinal tract, conjunctiva of the eye, and reproductive tracts.
What do goblet cells secrete?
Mucins, which hydrate to form mucus.
What is the role of the cup-like apical surface of goblet cells?
It stores mucin granules for secretion.
What distinguishes multicellular exocrine glands from unicellular glands?
Multicellular glands consist of secreting cells (adenomeres) connected to ducts.
What are intramural glands?
Glands located within epithelial tissue.
What are extramural glands?
Glands that form distinct organs, like the pancreas and salivary glands.
What are the three shapes of secretory units?
Tubular, alveolar (acinar), and tubuloalveolar.
What is a tubular gland?
A gland with a tube-shaped secretory unit.
What is an alveolar gland?
A gland with a round or sac-like secretory unit.
What are simple glands?
Glands with unbranched ducts.
What are compound glands?
Glands with branched ducts.
What is the difference between a simple gland and a simple branched gland?
Simple glands have one secretory unit, while simple branched glands have multiple secretory units connected to a single duct.
What are glands/secreting epithelia?
cells tightly apposed forming aggregates with different morphology
Molecules to be secreted can be stored in membrane-bound secretory granules (vesicles)
What are the three modes of secretion?
Merocrine, apocrine, and holocrine.
What characterizes merocrine secretion?
Secretory products are released via exocytosis without loss of cellular material.
Name examples of merocrine glands.
Salivary glands, pancreas, gastric glands, intestinal glands, lacrimal glands.
What characterizes apocrine secretion?
Secretions are released along with a portion of the apical cytoplasm.
Name examples of apocrine glands.
Mammary glands and some sweat glands.
What characterizes holocrine secretion?
The entire cell disintegrates to release its content.
Name an example of a holocrine gland.
Sebaceous glands.
What are the three types of secretions?
Serous, mucous, and mixed.
What are serous secretions?
Watery, enzyme-rich secretions.
What are mucous secretions?
Thick, viscous secretions rich in mucins.
What are mixed secretions?
A combination of serous and mucous secretions.
Give an example of a mixed gland.
Submandibular salivary gland.
What is the function of myoepithelial cells?
To contract and help expel secretions from glandular acini.
Where are myoepithelial cells found?
Surrounding the secretory units of glands like salivary glands and mammary glands.
What type of gland is the exocrine pancreas?
A compound tubuloacinar gland composed of serous secretory cells.
What does the exocrine pancreas secrete?
Digestive enzymes.
What are the smallest ducts in the exocrine pancreas called?
Intercalated ducts.
What is the major excretory duct of the pancreas?
The Wirsung duct.
Name a gland with simple tubular structure.
Crypts of Lieberkühn in the intestine.
Name a gland with simple acinar structure.
Small sebaceous glands.
Name a gland with compound alveolar structure.
Mammary glands.
Name a gland with compound tubuloacinar structure.
Parotid salivary glands.
What happens in cystic fibrosis in relation to exocrine glands?
Thickened secretions block ducts, particularly in the pancreas and respiratory tract.
How does a blockage in the Wirsung duct affect digestion?
It impairs the release of digestive enzymes, leading to malabsorption.
What feature distinguishes serous cells histologically?
Round nuclei and basophilic cytoplasm.
How are mucous cells distinguished histologically?
Flattened nuclei pushed to the base by mucinogen granules.
What is the role of basal infoldings in striated ducts?
They increase the surface area for ion transport.
What organelles are prominent in goblet cells and why?
Golgi apparatus for processing mucins and abundant rough endoplasmic reticulum (RER) for protein synthesis.
What happens to mucinogen granules in goblet cells during secretion?
They are hydrated upon exocytosis to form mucus.
How do goblet cells contribute to the respiratory system?
By trapping particles and microorganisms in mucus to protect the airway lining.
What is the function of ducts in multicellular glands?
To transport and modify secretions before delivery to target sites.
How are secretory units and ducts arranged in compound glands?
Secretory units form lobules, which drain into intralobular ducts, then interlobular ducts, and finally into major excretory ducts.
What distinguishes intralobular ducts from interlobular ducts histologically?
Intralobular ducts are smaller and often lined with simple cuboidal epithelium, while interlobular ducts have larger lumens and may have columnar epithelium.
Why are serous secretions watery?
They are rich in enzymes and have low mucin content.
What is the role of mucous secretions in the gastrointestinal tract?
To lubricate and protect the lining from digestive enzymes and acids.
How are mixed glands structured to produce both serous and mucous secretions?
They have separate serous and mucous cells, often with serous demilunes capping mucous tubules.
What is the function of striated ducts in salivary glands?
To modify electrolyte concentrations in saliva by active ion transport.
Why are mitochondria abundant in the basal infoldings of striated ducts?
To provide energy for ion transport mechanisms.
What enzymes are produced by the exocrine pancreas?
Proteases (trypsin, chymotrypsin), amylase, and lipase.
What are centroacinar cells in the pancreas?
Cells located in the center of the acini that contribute to ductal secretion.
What is the role of the intercalated ducts in the pancreas?
To secrete bicarbonate and water, neutralizing stomach acid in the duodenum.
How is the pancreas protected from self-digestion?
Digestive enzymes are stored as inactive zymogens and activated only in the duodenum by enterokinases.
What is the functional advantage of a branched duct system in compound glands?
It allows the collection and delivery of secretions from multiple lobules
Name the major types of compound glands and examples.
Compound tubuloalveolar (mammary gland), compound acinar (pancreas), compound tubular (cardiac glands).
How are lobes and lobules separated in compound glands?
By connective tissue septa containing blood vessels, lymphatics, and nerves.
What proteins are found in myoepithelial cells, enabling contraction?
Actin, myosin, and cytokeratin.
Why are myoepithelial cells considered epithelial in origin despite their contractile function?
They arise from epithelial precursors and retain epithelial characteristics.
What are the two main functional components of the pancreas?
The exocrine portion (producing digestive enzymes) and the endocrine portion (islets of Langerhans).
What is the structural unit of the exocrine pancreas?
The acinus, which is a blind sac of secretory cells.
What are intercalated ducts, and what is their role?
Small ducts that connect the lumen of acini to larger ducts, secreting bicarbonate and water.
How does the duct system branch in the pancreas?
Intercalated ducts → Intralobular ducts → Interlobular ducts → Major pancreatic duct.
What type of epithelium lines the ducts of the exocrine pancreas?
Simple cuboidal epithelium in intercalated ducts and simple columnar epithelium in larger ducts.
How do pancreatic secretions aid digestion?
Enzymes break down proteins, carbohydrates, and fats, while bicarbonate neutralizes stomach acid.
What happens in acute pancreatitis?
Premature activation of zymogens causes autodigestion of pancreatic tissue.
