glandular epithelium

what is the glandular epithelium?

a type of epithelium that is specialized to produce secretion

where does the glandular epithelium originate from?

originates from invaginated epithelial cells that leave the surface

where do glandular epithelium cells penetrate?

they penetrate into the underlying connective tissue, forming a basal lamina around them

parenchyma is what?

the secretory units and ducts of the gland

the stroma is what?

elements of the connective tissue in the gland

how are the ducts in the body classified?

• according to presence or absence of ducts

• according number of cells in the glands

• according to changes in the ducts during secretion

• according to nature of secretion

• according to shape of secretory unit

how are the glands classified according to presence or absence of ducts?

• endocrine or ductless glands

• exocrine glands

• mixed glands

what are endocrine glands?

• glands that have no excretory duct.

• well-vascularized, because the secretion product is eliminated directly into the internal environment (usually blood)

how are the cells arranged in endocrine glands?

they are arranged in islands

• ex: endocrine pancreas

they are arranged in cords

• ex: adrenal gland

they are arranged in follicles

• thyroid

what are the characteristics of ductless / endocrine glands?

• hormones are messenger molecules (first messenger)

• circulate in blood

• act on distant target cells

• target cells respond to the hormone, for which they have receptors

• the effects are dependent on the programmed response of the target cells

what are some examples of endocrine glands?

1. thyroid gland

2. parathyroid gland

3. thymus

4. adrenal gland

what are exocrine glands?

• they have ducts to carry their secretions

  • ex: salivary, sweat and sebaceous glands

exocrine glands can be what?

they can be unicellular or multicellular

what are mixed glands? what is an example of this?

possess both exocrine and endocrine functions, such as the pancreas, which contains both endocrine and exocrine cells.

• exocrine function of pancreas: secrete digestive enzymes

• endocrine function of pancreas: islet cells of Langerhans. are responsible for insulin and glucagon

how can exocrine glands further be classified?

• number of cells

• morphology of the duct

• secretory unit

what are unicellular exocrine glands?

• goblet cells

• simplest form and only found in exocrine glands

how are unicellular glands found? what is an example?

• represented by isolated secretory cells in an epithelium

  • ex: intestinal or respiratory

• a classic example of unicellular exocrine gland is the goblet cell, found scattered among epithelial cells lining the trachea, small intestine and colon

what stimulates the release of unicellular exocrine glands?

• it is stimulated by chemical irritation and parasympathetic innervations

what are multicellular glands?

• formed of many cells

• they are clusters of secretory units arranged in varying degrees of organization, and together function as secretory units.

• ex: salivary glands

how are multicellular glands further subdivided?

1. duct component

2. shape of their secretory unit

duct component of multicellular glands

simple: ducts do not branch

compound: their ducts branch

shape of multicellular glands secretory unit?

• tubular

• acinar (alveolar, resembling a grape)

• tubuloalveolar

how are exocrine glands classified according to changes in secretory cells?

1. merocrine

2. apocrine

3. holocrine

merocrine glands:

• no cellular change in secretory cells with no loss of cytoplasm

• ex: salivary and parotid glands

apocrine glands:

• the tips of the secretory cells of the glands are detached and come out with the secretory products of the gland

• ex: mammary glands secrete milk, which contains parts of the secretory cells

holocrine glands:

• the entirety of the secretory cells are destroyed and come out with the secretion

• ex: the cells of sebaceous glands may come out with their secretion

how are glands classified according to the nature of secretion into?

1. serous glands

2. mucous glands

3. mixed glands

serous glands:

secrete a product rich in proteins, such as salivary glands, which are rich in digestive enzymes

mucous glands:

secrete a product rich in glycoproteins called mucins, such goblet cells

mixed glands:

• muco-serous or sero-mucous, such as salivary glands

what are the shapes of the multicellular exocrine glands are?

1. tubular

2. acinar / alveola

3. tubuloacinar / tubuloalveolar

how many ducts do simple glands have?

one duct

what are the 3 types of simple glands with examples?

1. simple tubular glands

   • glands of small and large intestine

2. simple coiled tubular gland

   • only example is the sweat gland of the skin

3. simple branched acinar gland

   • sebaceous gland of the skin

what are the 3 types of compound glands with examples?

1. compound branched acinar gland

   • exocrine pancreas

2. compound branched tubular gland

   • sub mucosal mucous gland in the duodenum

3. compound tubuloacinar/alveolar glands

   • salivary glands