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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 • 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.