Body membranes Cover body surfaces Line body cavities

• Body membranes – Cover body surfaces – Line body cavities – Form protective sheets around organs • Two types of body membranes: • Epithelial membranes • Connective tissue membranes

Classification of Body Membranes • Epithelial membranes: – cover and lines the internal or external cavities – Composed of epithelial cells attaching to • underling tissue with the help of connective tissue layer – E. g. • Cutaneous membrane • Mucous membrane • Serous membrane

Epithelial membrane • Cutaneous membrane : skin • Dry membrane • Outermost protective boundary • Superficial epidermis is composed of – Keratinized stratified squamous epithelium • Underlying dermis is build from – dense connective tissue

Epithelial membrane • Mucous Membranes: • Surface epithelium attached to the underlying tissue with loose connective tissue • Lines all body cavities that open to the exterior body surface such as digestive, respiratory, urinary, reproductive tracts • absorption and secretion

Epithelial membrane • Serous Membranes: • Surface is a layer of simple squamous epithelium • Underlying layer is a thin layer of areolar connective tissue • Lines open body cavities that are closed to the exterior of the body • Serous membranes occur in pairs separated by serous fluid – Visceral layer covers the outside of the organ – Parietal layer lines a portion of the wall of ventral body cavity

• Specific serous membranes – Peritoneum • Abdominal cavity – Pleura • Around the lungs – Pericardium • Around the heart

Classification of Body Membranes • Connective tissue membranes: • Synovial Membranes – composed of areolar connective tissue layer – contains no epithelial cells – Lines fibrous capsules surrounding joints – Secretes a lubricating fluid to prevent friction

• Consists of skin and accessory structures • Such as hair, nails, and glands • Covers the outside of the body • Forms the boundary between body and external environment • Protects the body from the outside world

• Protection : Skin protects against abrasion, UV light, reduce water loss, prevent microorganism entry • Sensation: Has sensory receptors, detect heat, cold, touch, pressure, pain • Temperature regulation: By control of blood flow through skin, sweat glands • Vitamin D production: Skin produce Vitamin D – UV light • Excretion: Excrete through skin

• • • Covers the entire outer surface of the body Consists of two layers: Epidermis Dermis Epidermis: Superficial layer of epithelial tissue – Resists abrasion – Reduces water loss • Dermis: Deep layer of connective tissue – Structural strength • Hypodermis: – Loose connective tissue that connects skin to underlying structures (muscle or bone) – Not part of skin

Skin Structure • Epidermis – outer layer – Stratified squamous epithelium – Often keratinized (hardened by keratin) – Prevents loss of water – Avascular

• Epidermis – 5 layers • stratum basale: bottom most single layer attached to the dermis – Undergoes mitotic cell division and replaces top layers as they move up – Receive nourishment from the underlying dermis that contains capillaries • • Stratum Spinosum Stratum granulosum

• Epidermis – 5 layers • Stratum lucidum – Formed from dead cells of the deeper strata – Occurs only in thick, hairless skin of the palms of hands and soles of feet • • stratum corneum – Top layer exposed to sun is Rich in keratin protein – Constantly replaced as they get damaged – Several layers that are Dead cells

• Keratinocytes: Secrete protein called – keratin that gives toughness to skin • Melanocytes : produce melanin – Found in stratum basale – gives skin different shades of color • Amount of melanin produced depends upon – genetics and exposure to sunlight • Melanin is produced in response to – UV light to protect the DNA – Prevent skin cancer Skin Structure

Skin Color • Three pigments contribute to skin color: • Melanin – Amount and kind of melanin in epidermis – Yellow, brown or black pigments • Carotene – Orange-yellow pigment from some vegetables • Hemoglobin – Red coloring from blood cells in dermis capillaries – Oxygen content determines the extent of red coloring

• Dermis – Dense connective tissue made of collagen and elastin fibers – Decreases with aging leading to wrinkles – Collagen fibers give skin its toughness – Elastic fibers give skin elasticity – Maintains body temperature, – response to stimuli – Consists of two layers • Papillary layer • Reticular layer

• Dermis • upper papillary layer : contact with epidermis – Contains fingerlike projections, called dermal papillae, extend towards epidermis – In the palms, fingers, soles, and toes papillae forms friction ridges which improves the grip of hand feet – Supplied with receptors for various senses – Unique to each individual

• Dermis • Lower reticular layer in contact with underlying hypodermis – Carries the blood vessels, glands, nerves, pressure receptors, phagocytes

• Deep to skin • Not part of skin • Consists of loose connective tissue with collagen and elastic fibers • Main types of cells in hypodermis are: – Fibroblasts – Adipose cells – Macrophages • Hypodermis is also called – Subcutaneous tissue • Contains about one-half of body’s fat. Functions as – Energy source – Insulation – Padding

Appendages of the Skin • Skin appendages consists of: • Cutaneous glands : Are exocrine glands – Sebaceous glands – Sweat glands • Hair and Hair follicles • Nails

• Sebaceous glands – Found all over the body except palms and soles of the feet – They produce oily substance also known as sebum • It contains oil and fragmented cells • Lubricant for skin and protects the skin from dryness • Kills bacteria – Most have ducts that empty into hair follicles – Glands are activated at puberty • Skin during puberty is oily – Acne : overactive sebaceous glands leading to pimples

• Sweat glands : Widely distributed in skin. Two types – Eccrine: Open via duct to pore on skin surface • Found all over the body • Produce salty sweat that prevents bacterial growth • Regulate body temperature – Apocrine: Ducts empty into hair follicles • Found in axillary and genital areas • Secretion has fatty acids and proteins in addition to sweat • Begins working after puberty • Gives unpleasant odor

Sweat and Its Function • Composition – Mostly water – Some metabolic waste – Fatty acids and proteins (apocrine only) • Function – Helps dissipate excess heat – Excretes waste products – Acidic nature inhibits bacteria growth • Odor is from associated bacteria

Hair – – – Consists of hard keratinized epithelial cells Melanocytes provide pigment for hair color Present all over the skin except: soles, palms, lips, nipples Size and thickness varies depending on their location Texture( soft or rough) varies depending on the amount of keratin protein

• Hair is produced by hair follicle • Hair is divided into • Shaft • Root • Shaft- protrudes above skin surface • Root- located below skin surface • Root & shaft of hair are composed of dead keratinized epithelial cells

• Each hair consists of 3 concentric layers: – Central medulla – Cortex surrounds medulla – Cuticle on outside of cortex • Most heavily keratinized

• Hair follicle: Consists of – Epithelial root sheath – Dermal root sheath – Epithelial root sheath: – Composed of epithelial tissue – Forms the hair – Dermal root sheath: – Composed of dermal connective tissue – Dermal region supplies blood vessels to epidermal portion

Associated Hair Structures • Arrector pilli – Smooth muscle cells – connect each side of the hair follicle – When this muscle is pulled, makes the hair stand erect and gives raise to goose bumps – Protects from loose of heat from the body

v Nail is protecting covering of distal part of finger or toe v Tool for pick up small objects, scratching v Nail contains a hard keratin v Each nail has a – free edge – a body (visible portion) – proximal root (embedded in the skin)

Nail Structures – Free edge: sharp – Body: visible and attached to underlying skin – Root of nail: hidden beneath the skin and rich in stratum basale epithelial cells – Responsible for nail growth – Eponychium – proximal nail fold that projects onto the nail body

Skin Homeostatic Imbalances • Infections – Athletes foot: • Caused by fungal infection – Boils and carbuncles • Inflammation of hair follicle and sebaceous gland • Effects neck and back • Carbuncles result from multiple boils • Caused by Staphylococcus aureus bacterial infection

Skin Homeostatic Imbalances • Infections – Cold sores • Fluid filled blisters • Around lips and oral cavity • Caused by herpes simplex virus • Contact dermatitis • Itching, redness and swelling leading to blisters • Exposures of chemicals cause allergic reaction

– Impetigo • Water filled lesion • Caused by contagious staphylococcus bacterial infection – Psoriasis • Cause is unknown • Chronic condition due to overproduction of skin cells leading to epidermal lesions and scaling • Triggered by trauma, infection, stress

• Burns – Damage to the skin – Tissue damage and cell death caused by heat, electricity, UV radiation, or chemicals – Resulting in Dehydration: due to loss of fluids from the surface of the burned skin leading to • Electrolyte imbalance : due to kidney function shut down • Circulatory shock : due to low blood volume

Rule of Nines: used to determine extent of burns • Body is divided into 11 areas for quick estimation – Each area represents about 9% – In addition to 1% of genital area • Burned tissue easily get – bacterial and fungal infections – Due to impaired immune system

• First-degree burns – Only epidermis is damaged – Skin is red and swollen – Heal with in few days with no scars – E. g sun burn • Second degree burns – Epidermis and upper dermis are damaged – Skin is red with blisters – Regenerate with in few weeks and scars are not present Severity of Burns

• Third-degree burns – Destroys entire skin layer ( epidermis and dermis) – Burn is gray-white or black – Nerve ending are also destroyed – Regeneration is not possible – Skin grafting is essential Severity of Burns

Critical Burns • Burns are considered critical if: – Over 25% of body has second degree burns – Over 10% of the body has third degree burns – third degree burns of the face, hands, or feet • Face: restricts movement of air through respiratory tract • Hands and feet: joint tissue repair limits joint mobility

Skin Cancer • Cancer ( neoplasm or tumors)– abnormal cell mass • Two types – Benign • Does not spread (encapsulated) – Malignant • Metastasized (moves) to other parts of the body • Skin cancer is the most common type of cancer

• Basal cell carcinoma – Least malignant – Most common type – Arises from stratum basale – Spread into dermis – Slow growing and does not undergo metastasis – surgery Skin Cancer Types

Skin Cancer Types • Squamous cell carcinoma – Arises from stratum spinosum – Sun induced commonly seen in areas such as hands, lips, scalp, ears – Develops into ulcers – Metastasizes to lymph nodes – Early removal allows a good chance of cure – Surgery or radiation

Skin Cancer Types • Malignant melanoma – Most deadly of skin cancers – Cancer of melanocytes – Appears as a black patch that seems to be growing – Metastasizes rapidly to lymph and blood vessels – Detection uses ABCD rule – Early detection helps in increasing the chances of survival

ABCD Rule • A = Asymmetry – Two sides of pigmented mole do not match • B = Border irregularity – Borders of mole are not smooth • C = Color – Different colors in pigmented area • D = Diameter – Spot is larger then 6 mm in diameter