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Skin and Body Membranes – Part 1

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1 Skin and Body Membranes – Part 1
Chapter 4

2 Body Membranes Body Membranes – Cover surfaces, line body cavities, and form protective sheets around organs. Two major groups of body membranes: Epithelial membranes Connective tissue membranes

3 Epithelial Membranes Include:
Cutaneous Membranes Mucous Membranes Serous Membranes All contain an epithelial sheet combined with an underlying layer of connective tissue. These membranes are actually simple organs.

4 Cutaneous Membranes Cutaneous Membrane – Skin
Its superficial epidermis is composed of a keratinizing stratified squamous epithelium. The underlying dermis is mostly dense connective tissue. Is exposed to air and is a dry membrane.

5 Mucous Membrane Mucous Membrane (Mucosa) – Lines all body cavities that open to the exterior (digestive, urinary, respiratory). Composed of epithelium resting on a loose connective tissue membrane. Most contain either stratified squamous epithelium or simple columnar epithelium.

6 Mucous Membranes They are “wet” or moist membranes that are always continuously bathed in the secretions or urine. Mucosae of the digestive and respiratory tracts secrete mucus. Mucosae of the urinary tract produces urine. Often adapted for absorption or secretion.

7 Serous Membranes Serous Membranes – Line body cavities that are closed to the exterior. Exceptions: Dorsal body cavity and joint cavities Composed of a layer of simple squamous epithelium resting on a thin layer of areolar CT.

8 Serous Membranes Occur in pairs
The parietal layer lines a specific portion of the wall of the ventral cavity. The parietal layer folds in on itself to form the visceral layer, which covers the outside of the organs in that cavity.

9 Serous Membranes Similar to you pushing your fist into a limp balloon.
Visceral Serosa = Part of the balloon that clings closely to your fist. Parietal Serosa = Outer wall of the balloon.

10 Serous Membranes The serous layers are separated by a thin, clear fluid called serous fluid. Serous fluid is secreted by both membranes. Two layers lie very close to each other. The fluid allows the layers to slide easily across the cavity walls and one another.

11 Serous Membranes: Examples
Peritoneum – Serosa lining the abdominal cavity and covering its organs. Pleura – Serous membrane that surrounds the lungs. Pericardium – Serous membrane that surrounds the heart.

12 Connective Tissue Membranes
Synovial Membranes – Composed of soft areolar CT and contain no epithelial cells at all. Cushion organs moving against each other during muscle activity (such as the movement of a tendon across a bone’s surface).

13 Where are Synovial Membranes Located?
Line the fibrous capsules surrounding joints. Provide a smooth surface and secrete a lubricating fluid. Also line small sacs of CT called bursae and the tubelike tendon sheaths.

14 Integumentary System (Skin)
Skin (Integument) – Cutaneous membrane; External covering of the body. Integumentary System – The skin and its derivatives (sweat and oil glands, hairs, and nails).

15 Skin Absolutely essential because it keeps water and other precious molecules in the body. It also keeps water and other things out. Pliable, yet tough, which allows it to take constant punishment from external agents. Without our skin, we would quickly fall prey to bacteria and perish from water and heat loss.

16 Functions of the Skin Protects the entire body from:
mechanical damage (bumps and cuts) chemical damage (such as from acids and bases) thermal damage (heat and cold) ultraviolet radiation (sunlight) bacteria Insulates and cushions the deeper organs.

17 Functions of the Skin (Continued)
Acts as a mini-excretory system. Urea, salts, and water are lost through sweat. Manufactures several proteins important to immunity and synthesizes vitamin D. Sensory receptors provide us with a great deal of information about our external environment.

18 The Main Layers of Skin Epidermis Dermis
Hypodermis or Subcutaneous Tissue

19 The Main Layers of Skin Epidermis Dermis
The outer layer of the skin. Made up of stratified squamous epithelium that is capable of keratinizing, or becoming hard and tough. Dermis The inner layer of the skin. Made up of dense CT. Hypodermis or Subcutaneous Tissue Subcutaneous layer of fat and loose connective tissue that help insulate the body and acts as a shock absorber. Not considered part of the skin, but it does anchor the skin to underlying organs.

20 Blisters The epidermis and dermis are firmly connected.
Friction or a burn may cause them to separate and results in a blister.

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