Histology II:Glands and membranes

Histology II:Histology II:Glands and membranesGlands and membranes

Dr. Carmen E. RexachAnatomy 35

Mt San Antonio College

Gland• Cell or organ that secretes substance• Tissue

– Epithelial– Supportive CT

• Endocrine vs. exocrine– Endocrine

• Secrete hormones• No contact with surface• No ducts• Invaded by capillaries• Secrete products into blood

– Exocrine• Ducted to surface or into a lumen

Exocrine glands• Unicellular

– Ex) goblet cells• Multicellular

– Secretory portion– Ductal portion– Larger glands usually lined by stratified

epithelium

Unicellular Exocrine Glands

Goblet cells

Multicellular Exocrine Glands• Acinar

– pyramid shaped cells– form rings called acini

• Tubular– cuboidal cells

Classification by duct structure

• Simple– Unbranched duct– Straight or coiled– Tubular gland = if secretory portion is tube

shaped• Compound

– Duct displays repeated branching pattern

Branching patterns

• Simple

• Branched

• Compound branching

Classification by mechanism of secretion

• Merocrine• Apocrine• Holocrine

Merocrine• Majority of glands in body• Secretion by exocytosis

without any loss of cellular components

• Examples– Salivary glands– Pancreatic acini

Apocrine• Secretion includes

partial cell loss• Products are milky• Most glands originally

classified as apocrinehave been reclassified as merocrine

• Cellular products support bacterial growth so that these secretions are often associated with an odor

Holocrine• Entire cell is secretory

product• Oily, waxy product• Sebaceous and

ceruminous glands• Secretions = sebum

Epithelial Membranes• Line body “tracts” and surrounding

organs– protective membranes composed of CT

covered with epithelium.– (1) Mucous membranes– (2) Serous membranes

(1) Mucous membranes (mucosae)• Line passageways opening to exterior

– digestive, respiratory, urinary, reproductive tracts

• Goblet cells secrete mucus • Functions:

– Absorption– Secretion– Protection

• Two to three layers– Epithelium (columnar or squamous)– Lamina propria

• Areolar CT– Muscularis mucosae

(2) Serous membranes• Serosa secrete serous fluid derived

from serum• covering and lining epithelium

– simple squamous epithelium on thin layer of areolar CT

– Two parts• Visceral

– Covers organs• Parietal

– Loose fitting fibrous CT lines body walls

– Ex) pericardium, peritoneum, pleura

Pericardium

Parts of the peritoneum

• Mesenteries– where parietal portions of the peritoneum

come together (attach) the organ to the posterior body wall

• omenta (omentum s.)– folds of the peritoneum that extend from

the stomach

mesentery

greater omentum

Lesser omentum

Serous membranes associated with the liver

• falciform ligament– a serous membrane suspending the liver

from the diaphragm• ligamentum teres hepatis

– extends from the falciform ligament to umbilicus

Additional epithelial membranes

• Endothelium– Simple squamous epithelium lining blood

vessels– Tunica interna of blood vessels and

endocardium of the heart• Mesothelium

– Simple squamous epithelium lining pleura, peritoneal cavity and pericardial cavity