Topic Set 5: Cell Junctions & Glandular Epithelium

What is a cell junction?

A point of contact between plasma membranes of adjacent cells

What is the structure of a tight junction?

Transmembrane proteins fuse neighboring plasma membranes like a zipper

What is the function of a tight junction?

Forms a permeability barrier to limit transport

Where is the adhesion belt located relative to the tight junction?

Just inferior (below) to the tight junction

What is the function of an adhesion belt?

Anchors epithelial cells together and adds strength to tight junctions

What is the structure of a gap junction?

Protein channels between cells

What is the function of a gap junction?

Allows for quick and easy transport

What is the structure of a desmosome?

Attaches to the cytoskeleton of neighboring cells like a button

What is the function of a desmosome?

Prevents cells from separating

Where are desmosomes commonly found?

In stratified epithelial tissues and cardiac muscle

What is a hemidesmosome?

1/2 of a desmosome

What is the function of a hemidesmosome?

Connects cells to the basement membrane

What is a gland?

A secretory organ that makes and secretes a product

What are the two main types of glands?

Endocrine glands and exocrine glands

What are endocrine glands?

Ductless glands that produce hormones

Where do endocrine glands release their product?

Into the blood

What are exocrine glands?

Glands that have a duct

Where do exocrine glands release their product?

Onto an epithelial cell surface

What type of glands are most glands?

Multicellular

What type of gland are goblet cells?

Unicellular glands

What are simple exocrine glands?

Multicellular glands with a single, unbranched duct

What are compound exocrine glands?

Multicellular glands with a duct that has many branches

What are the structural variations of simple exocrine glands based on shape?

Simple tubular, simple coiled tubular, simple branched tubular, simple alveolar, and simple branched alveolar

What are the structural variations of compound exocrine glands based on shape?

Compound tubular, compound alveolar, and compound tubuloalveolar

How is secretion packaged in merocrine secretion?

Packaged into vesicles

How is secretion released in merocrine secretion?

By exocytosis

What are examples of merocrine glands?

Salivary glands, lacrimal glands, and sweat glands

Where does secretion accumulate in apocrine secretion?

In the top of the cell

How is secretion released in apocrine secretion?

Top portion of the cell pinches off

What are examples of apocrine glands?

Mammary glands and ceruminous glands

What causes the release of the secretory product in holocrine secretion?

Cell ruptures and dies

How are ruptured cells replaced in holocrine secretion?

By mitotic activity

What is an example of a holocrine gland?

Sebaceous glands