INTEGUMENTARY SYSTEM

SKIN &BODY MEMBRANES

MEMBRANES: An overview• Defined:

– Superficial layer of epithelial cells– underlying layer of supportive connective tissue

• Structure: Thin, sheet-like structure

Membranes: Functions

• Functions:– Cover and protect the body surface, internal

organs– Line the body cavities, inner surface of hollow

organs– Anchor organs to each other or to bones– Secrete lubricating fluids that reduce friction

during organ movements

Two Types of Body Membranes

• 1) Connective Tissue Membranes• 2) Epithelial Membranes

– Serous membranes– Mucous membrane– Cutaneous membrane (skin)

Connective: Synovial Membrane

• Structure– No epithelial layer –

connective only– Smooth & slick

Connective: Synovial Membrane

• Function: – Lines capsules b/w joints that move– Lines bursa sacs– Secrete synovial fluid– Reduce friction b/w opposing bones

Epithelial: Serous Membranes• Found only on surfaces within closed cavities• 2-layer structure:

– Epithelial – thin layer of simple, squamous epithelium

– Connective – thin, glue-like basement membrane that holds and supports

Serous Membranes: Function

• Function: Protection/reduce friction for organs• Two Types (1 continuous layer):

1. Visceral: covers the surface of the organ2. Parietal: lines the walls of the body cavity

• Thoracic Cavity/Lungs=Pleura• Abdominal Cavity=Peritoneum

– What is pleurisy? – What is peritonitis?

Epithelial: Mucous MembraneSecretes Mucus: moistens, lubricates, protectsLines body surfaces opening directly to exterior

(respiratory, digestive, reproductive & urinary tracts)

Structure: - Epithelium varies depending on location,

function

Epithelial: Mucous Membranes

Epithelial: Cutaneous Membrane

• = Skin

Epithelial: Cutaneous Membrane (SKIN)

• FUNCTIONS– Protection against microbes, UV rays, harmful

chemicals, cuts & tears– Temperature regulations– Sense organ activity: touch, pressure, pain,

temperature– Metabolic functions: synthesis of vitamin D

Skin: Structure• Structure: 2 Layers:

1. Epithelial: Epidermis • outermost & thinnest• cells are very tightly packed

2. Connective: Dermis • deep & thick• primarily connective tissue• loosely packed

• Hypodermis (adipose tissue)– Deep to the skin/dermis– Layer of insulation

Epidermis• Outermost: Stratum

corneum– Dry, dead, – keratin filled (waterproof,

tough)• Statum germinativum /

basale– Cells undergoing mitosis,

move up – “Pigment layer”

http://en.wikipedia.org/wiki/Image:Skinlayers.png

Stratum corneum: Dead squamous cells

Stratum Germanitivum/Basale: dividing columnar cells

Stratum Spinosum: cuboidal cells, desmosomes hold together >> spiny

Stratum granulosum: Granules with lipids and keratin – forms waterproof layer

Stratum lucidum: oils from lysosome disintegration

Epidermis

• Specialized cells within epidermis:– Melanocytes

• Melanin: pigment, inc. w/sun (protection)– Keratinocytes

• Keratin: tough, waterproof material; abrasion resistance for cells

– Langerhans cells• Immune response against microbes invading the skin