Skin and Body Membranes Chapter 4

1. Skin and Body Membranes Chapter 4

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

3. 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

4. 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

5. 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

6. 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

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

8. 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

9. Integumentary System • 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

10. Functions of Integumentary System • 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

11. 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

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

13. 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

14. 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

15. Skin Structure • 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

16. 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

17. 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

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

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

20. Hypodermis • 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

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

22. 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

23. 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

24. 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

25. 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

26. Hair Structure • 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

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

28. Hair Structure • 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

29. 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

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

31. 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

32. 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

33. 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

34. 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

35. 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

36. 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

37. Severity of Burns • 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

38. 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

39. 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

40. 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

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

42. 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

43. 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

44. 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