Three Types of Membrane

1. Cutaneous membranes = skin = Integumentary system.  We have the epidermis which is the outer epithelium tissue and dermis is the connective tissue.

2. Mucous (mucosa) membranes line the insides of hollow organs that open to the outside.  (Mouth, rectum, reproductive, urinary)

3. Serous membrane (serosa/serosae pl.)

Three closed cavities: Pleural (lungs), peritoneal (abdominal), and pericardial (heart) cavities.
Serous is made up of filtrate leaked from the capillary blood in the connective tissue plus lubricating molecules secreted by the mesothelial cells.
Parietal layer lines cavity; Visceral layer covers organs (visceral=inside)

Capacity for regeneration

Good to excellent: Epithelial tissue, bone CT, areolar CT, dense irregular CT, and blood forming CT
Moderate: Smooth muscle (intestine), dense regular CT (like the tendon)
Weak: Skeletal muscle tissue and cartilage.
None: Cardiac muscle tissue, nervous tissue.  When cardiac muscle dies it becomes scar tissue.  That’s why it’s so bad for you to have a heart attack.  Same goes for nerve tissue, although it is possible to transplant brain matter and retrain a person.  But wherever there are slices in the spinal cord we cannot repair them.

Tissues throughout life

By the end of the second month of pregnancy, the four primary tissues have formed and all major organs are in place.

Your bones, muscles and nervous tissue will atrophy due to less use as you age.  If you stay active though, they won’t.

Collagen tends to decrease and the epithelial lining thins out.

Poor nutrition and circulation tax the body, eventually creating health complications over decades of misusing the body.

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Painting by Michael Reedy
The Basics. Start here. This is your Foundation.


The Autonomic Nervous System

Specialized Systems