Respiratory and Digestive System

Lumen

A cavity or hole inside of a tube, blood vessel or hollow organ

‘Blood flows through the ______ of a blood vessel’

Acini

A small, ball-shaped cluster of secretory cells surrounding ducts

Duct

A tubular structure that transports secretions of a gland

Comprised of simple cuboidal epithelium, arranged in a doughnut pattern

Lobes

Large, roundish projections or divisions of an organ

Can be seen with the naked eye

Lobules

Small divisions of the cells in an organ, forming a functional unit

Usually require a microscope to be seen

Serosa

Very thin tunic made of simple squamous epithelium that surrounds the outside of the organ

Difficult to see but always present

Muscularis Externa

Lies immediately inside the serosa

Two layers of smooth muscle

Outside fibers longitudinally - inside fibers circularly

Help in peristalsis - wavelike movement forcing food through

Submucosa

Lay next to the muscularis externa

Rather empty; only contains scattered nuclei, wavy collagen fibers and glandular tissue

Mucosa

Closest to the lumen

Composed of muscularis mucosa, lamina propria, and epithelium

Muscularis mucosa

Outer layer of mucosa

Very thin layer of smooth muscle, distinct as a dark pink band

Lamina propria

Middle layer of mucosa

A loose matrix of cells and ground tissue

Epithelium

Innermost layer of mucosa

Protects the organ from the contents in the lumen

Mucosa, submucosa, muscularis externa, serosa

Deep → superficial Alimentary Canal

Serosa, muscularis externa, submucosa, mucosa

Superficial → Deep Alimentary Canal