Chapter 4: glands, cell junctions, and membranes

most glands are composed of:

epithelial cells

what kind of things do glands secrete?

specific secretions

• ex) sweat, milk, hormone, enzyme

goblet cells (+ location)

single celled glands that secret mucus

• in respiratory and digestive tracts

are glands unicellular or multicellular?

some unicellular (like goblet cells), most multicellular

categories of multicellular glands

exocrine and endocrine

endocrine glands

groups of secretory cells surrounded by a rich network of capillaries that secrete hormones into the blood

how are exocrine glands related to the epithelium?

they retain a connection to the epithelium from which they originate; the connection is a duct that carries the secretions

simple glands structure

single, unbranched duct

simple (and compound) glands secretory main forms

• tubular (alveolar)

• acinar (rounded)

• tubuloacinar (both)

compound glands structure

branched

most common compound gland type

compound tubuloacinar

compound tubuloacinar locations

prostate, pancreas

functional classification of exocrine glands

• meocrine

• apocrine

• holocrine

most common mode of secretion (exocrine)

meocrine

meocrine secretion

secretion via exocytosis (no cell distruction)

meocrine secretion locations

pancreas, salivary glands, most sweat glands

apocrine secretion

apycial cytoplasm with secretory vesicles is shed

apocrine secretion locations

axillary and anal sweat glands, mammary glands

holocrine secretion

secretion accumulates in the cells, then the cells rupture and die, releasing the secretion along with lipids from the plasma membrane

• new cells replace old

holocrine secretion location

sebaceous (oil) glands of skin

cell junctions (+ functions)

attachments of cells

• stress resistance

• facilitate communication

tight junction

they encircle epithelial cells near apex, forming a tight attachment to neighbors that seals intracellular space and makes it difficult for substances like HCl or bacteria to pass through cells and invade the underlying tissue

adherens junctions

form adhesion belts

adhesion belts

formed by adherens junctions

desmosomes

“spot welds” between cells

hemidesmosomes

attach cells to extracellular structures (like the basement membrane)

gap junctions

communicating junctions; allows substances to pass from

mucous membranes (mucosa) (+ locations)

moist epithelial membranes lining the cavities opening to outside

• digestive, respiratory, urinary, reproductive tracts

mucous

viscous fluid which protects and lubricates, secreted by the mucous membrane (and goblet cells)

mucous membrane (mucosa) layers

• free surface: epithelium

• next layer: lamina propria (loose CT supporting epith.)

• deepest layer: muscularis mucosa (thin layer of smooth muscle)

lamina propria

middle layer in the mucosa made of loose CT that supports the epithelium

muscularis mucosa

the deepest layer of the mucosa, a thin layer of smooth muscle

serous membranes (serosae) (+ locations)

epithelial membranes lining the ventral body cavities which do NOT open to the exterior

• parietal and visceral parts of the pleura, pericardium, and peritoneum

serous membrane layers

• free layer: simple squamous epithelium (mesothelium)

• next layer: thin layer of areolar CT

mesothelium

the simple squamous epithelial free layer of the serous membrane

serous membrane secretion (and what secretes it)

serous fluid, secreted by mesothelium cells

cutaneous membrane (+ layers)

skin

• stratified squamous epithelium (epidermis)

• areolar + dense irregular CT (dermis)

synovial membrane

lines joint cavities (NOT epithelial membrane)

synovial membrane secretion

synovial fluid

what is the only non-epithelial membrane

synovial