4.2 continued Human Structure and Function

Simple Squamous Epithelium

Cells flattened laterally, smaller cytoplasm, found where filtration or exchange of substances by rapid diffusion takes place

Two types of Simple Squamous Epithelia

Endothelium, Mesothelium

Endothelium

Friction-reducing lining in lymphatic vessels and cardiovascular system

Mesothelium

Found in membranes lining the ventral body cavity and its organs

Simple Cuboidal Epithelium

Single layer of cubed cells, secretion and absorption, found on walls of small duct glands and kidney tubules

Single Columnar Epithelium

Single layer of tall closely packed cells, lines digestive tract from stomach through rectum, absorption and secretion

Stratified Squamous Epithelium

Several layers, thick, protects, found in areas vulnerable to cells being worn down

Stratified cuboidal epithelium

Rare, two layers of cuboidal cells, found in ducts of larger glands,

Stratified columnar epithelium

Rare, multiple cell layers, only top one columns, found in pharynx, male urethra, lining gland ducts, and junction between other epithelia

Gland

One or more cells that make a secrete a particular product

Secretion

Active process, refers to both glands product and process of making and releasing that product

Two types of glands

Endocrine, Exocrine

Endocrine

Internally secreting, secrete directly into bloodstream, make hormones, can be single or multi cellular

Exocrine

Externally secreting, secrete products onto body surface or cavities, unicellular do it directly, multicellular need epithelium duct that transports

Goblet cells

Unicellular, accumulate and make mucin which makes makes mucus

Mucus

Unicellular, lines and protects body organs and systems, made of mucin, complex glycoprotein

Multicelular exocrine glands

Has epithelium-delivered duct and secretory unit, connective tissue supplies with blood vessels and nerve fibers to from fibrous capsle

Multicellular exocrine glands 2 structural classification

Simple glands, compound, tubular, alveolar

Simple Glands

Unbranched duct

Compound glands

branched duct

Tubular glands

Secretory cells form tubes

Alveolar/ acinar glands

Secretory cells form small sacs

Multicellular glands 2 types of modes of secretion

Merocrine glands, holocrine glands

Merocrine glands

secrete products by exocytosis, as they are produced

Holocrine glands

Cell fills up with substances and dies, releasing it