visceral system

viscera

• organs that regulate internal environment

• occupy cavities of body: thorax, abdomen, pelvis. also neck and head

• involved with secretion, excretion, digestion, absorption

• can be hollow or solid

hollow viscera

Levels:

• lumen

• mucosa

• muscularis

• serosa (external layer) - minimises friction

muscle coats

wall: circular and longitudinal smooth muscle

• provides motility and expansion

lumen of tubular (hollow) viscus

• may have dilations and constrictions

• constrictions - at end and beginning and also at specific sites

• narrow where it approaches the wall of hollow viscus

sphincter

1) anatomical: localised muscle thickening around wall of tubular viscus - controls passage and prevents reflux of contents

• can be voluntary (made of skeletal muscle, somatic NS) or involuntary (made of smooth muscles, autonomic NS)

2) functional: no localised muscular thickening

solid viscera

Glands: cluster of secretory cells

eg: pancreas, liver, thyroid gland

• external capsule (protection) and serosa (reduces friction)

• may have subdivisions: outer cortex, inner medulla

exocrine vs endocrine glands

exocrine glands:

• glands that secrete into a duct or system of ducts

• ducts emmerge from hilum of viscera

• open into hollow viscera

• eg: liver and bile duct

endocrine glands:

• glands that secrete directly into blood stream

• usually secrete hormones that act in other parts of body

• rich blood supply

• eg: adrenal glands

pancreas is both exocrine and endocrine

serous membrane

• single membrane that lines a body cavity and contains a space within it

• provides fluid which lubricates the cavity

• lines body wall

• covers or all of a viscus

• subdivided into parietal and visceral layers

eg: pleura and pericardium in thoracic cavity

peritoneal cavity

a closed cavity in the abdomen lined by a serous membrane called the periotoneum

role of mesentrey

a mesentery provides viscus with:

1) a pathway for nerves and vessels

2) mobility

referred pain

is the perception of pain in areas other than the site of stimulation.

• visceral pain is usually referred to somatic regions