Integumentary System

Home , Stratum basale, Stratum granulosum, Stratum lucidum, Stratum spinosum

Chapter 5 Integumentary System Integumentary system consists of: 1) Skin….the cutaneous membrane-Composed of epidermis and dermis 2) Accessary structures- hair, nails, glands.

Dermatology: branch of medicine that deals with the diagnosis and treatment of skin disorders.

Epidermis

Papillary layer Dermis Reticular layer

Hypodermis

Fat

Hypodermis/subcutaneous layer- NOT a part of the skin: - attaches skin to the muscle underneath. - contains blood vessels and nerves and large amount of adipose tissue - permits independent movement of deeper structures Functions of Skin 1) Protection: Stratified squamous epithelium….protects from abrasions. Sweat and oils….protects from bacterial infections. Keratin….water-proofing protein….prevents dehydration. Melanin….brown pigment….protects from UV exposure. 2) Thermoregulation: Sweat glands….evaporation of sweat  cooling. Blood vessels  vasoconstrict/vasodilate  control blood flow in the skin  heat loss/conservation. 3) Sensation: Nerve endings…sense temperature, touch, pressure, pain. Abundant in skin of the face, fingers, nipples, genitals. Fewer in skin of the back, knees, elbows. 4) Excretion: sweat…water, salt, organic substances. 5) Fat storage: adipose tissue in skin and subcutaneous layers. 6) Immunity: WBCs in skin….protect from infections. 7) Blood reservoir: blood vessels in skin hold 5% blood  can be diverted to other organs. 8) Synthesis of vitamin D: skin, kidneys, liver together  help make vitamin D  used to absorb Ca  bone development and maintenance. 9) Communication: facial expression, reflection of age, emotions. Structure of Skin

Epidermis

Papillary layer Dermis Reticular layer

Hypodermis

Skin is composed of two layers: 1) Epidermis – top layer of the skin. Skin is defined as thin or thick based on the epidermis: Thinner in thin skin (most of the body) and thicker in thick skin (palm, soles).

2) Dermis – lower layer of the skin. Epidermis

Epidermis

Papillary layer Dermis Reticular layer

Hypodermis

Fat I) Epidermis : Made of stratified squamous epithelium…accommodates wear/tear. Avascular…blood vessels only till the base layer…cells are fed by diffusion. Nerve endings end at the base of epidermis…limited to dermis. It is 4 layered in thin skin. It is 5 layered in thick skin. Epidermis

Thin skin: Thick skin: Covers most of the body. Covers palms and soles. Composed of 4 layers: Composed of 5 layers: Stratum corneum Stratum corneum Stratum granulosum Stratum lucidum Stratum spinosum Stratum granulosum Stratum basale Stratum spinosum Stratum basale Study each layer….going from the bottom layer  top layer. Epidermis

Stratum basale: bottom/deepest layer Consists of: a) Stem cells  divide by mitosis  new cells: b) Melanocytes  make melanin (brown pigment) give color to the skin. c) Merkel/Tactile cells  touch sensation. Epidermis

Stratum spinosum: second layer from the bottom…derived from stratum basale cells. Consists of: a) Keratinocytes-makes keratin (water-proofing protein)  prevents water loss through skin…prevents dehydration.

b) Langerhans/Dendritic cells  immune cells that protect against infections. Epidermis

Stratum granulosum: third layer from the bottom…derived from stratum spinosum.

Consists of: Flattened Keratinocytes…3-5 layers of cells  accumulate keratin. Epidermis

Stratum lucidum: - Absent in thin skin. - Found only in thick skin of palm and sole. - Consists of 3-5 rows of flattened dead keratinocytes that further accumulate keratin. Epidermis

Stratum corneum: -Top layer of the epidermis. -Thicker in thick skin of palm and sole….thinner in thin skin. - Consists of rows of completely dead cells. - Packed (15-30 layers) with keratin-Responsible for water resistance -Forms tiny specks/clusters – dander  continuously fall away – exfoliation. Dermis

Epidermis

Papillary layer Dermis

Reticular layer

Hypodermis

II) Dermis – lower layer of the skin-Made of fibrous connective tissue, blood vessels and nerves. Also has glands and hair follicles. - Although not used to define thick vs. thin skin, it is thinner in thin skin and thicker in thick skin - Dermis is made of 2 regions: 1) Papillary region- upper, thinner region of dermis. 2) Reticular region- lower, thicker region of dermis. Dermis

Epidermis

Papillary layer Dermis Reticular layer

Hypodermis

Fat Dermis : 1) Papillary region- upper, thinner region of dermis. -Forms finger-like projections – dermal papillae Project into epidermis  forms epidermal ridges (fingerprints reveal the pattern of epidermal ridges). Dermis

Epidermis

Papillary layer Dermis Reticular layer

Hypodermis

Dermis : 2) Reticular region- lower, thicker region of dermis. - Contains accessory structures – glands and hair follicles. - Collagenous fibers are arranged in parallel bundles  establishes cleavage or tension lines. Dermis

Bedsores/Decubitis ulcers: Comatose patients  dermal blood vessels in papillary and reticular layers of dermis are pressed against deeper layers  blood supply cuts off  epidermis and dermis dies (necrosis)  infection…open sores…ulcers. Skin Color Primary pigments found in epidermis:-

1. Melanin: brown color

2. Hemoglobin: red color from the blood

3. Carotene: yellow color Skin Color 1. Melanin: a) Brown color pigment produced by melanocytes present in stratum basale of epidermis. b) Number of melanocytes is similar in different races, only the levels of melanin synthesis is different. c) Melanin protects epidermis and dermis from harmful effects (UV) of sunlight

Melanin production is controlled by: A. Genetics – affects the amount of melanin produced, its distribution, and the rate at which it is broken down. B. Exposure to UV  more melanin produced  skin becomes darker – skin tan C. Hormone MSH – produced by pituitary gland  stimulates melanocytes to synthesize and distribute.

melanin pigment

melanocyte Skin Color

2. Hemoglobin-Blood contain red blood cells filled with hemoglobin More capillaries in dermis and thinner epidermis  redder the skin. Skin Color

3. Carotene: yellow color from the pigment. - Pigment found in yellow fruits and vegetable - Can make vitamin A. -Greater consumption of carotene  pigment accumulates in stratum corneum and subcutaneous fat  yellow hue in Asian skin. Skin Color Disorders a)Albinism: melanocytes are present, but melanocytes cannot make melanin absence of melanin production- no color in skin, hair or eyes. b) Vitiligo: partial or complete loss of melanocytes  patchy white spots on skin. c) Freckles and moles: overproduction of melanin in areas  melanin accumulates in patches. d) Hemangiomas: too many blood capillaries in dermis  patches of red-purple called strawberry birthmarks or also called port wine stains. May disappear during early childhood years or last life long. Vitiligo

Albinism

Freckles Hemangioma Skin Color Clues Skin color clues: help detect certain physiological disorders or conditions.

1) Cyanosis- bluish skin color…oxygen deficiency…hemoglobin turns darker red  reflects bluish through the skin-due to respiratory obstruction/arrest, heart failure, exposure to extreme cold.

2) Jaundice- yellow skin color-liver cannot excrete bile (bilirubin)-due to liver disorder (hepatitis, cancer, cirrhosis), blood infections or blood group issues at birth

3) Erythema- red skin color…vasodilation due to exercise, high temperature, anger, embarrassment, heatstroke.

4) Bruise- blood vessel break  bleeding  hematoma under the skin  changes from red to blue to yellow  slowly fades away.

5) Pallor- pale skin…due to temperature drop, anemia, low blood pressure, emotional stress.

Cyanosis Jaundice Bruise Skin – Vitamin D Synthesis & Ca Absorption

Limited exposure to sunlight is beneficial! Exposure of skin to UV  Skin epidermis (stratum basale and spinosum) use steroids to make vitamin D3 or cholecalciferol  Liver converts it to an intermediary compound  Kidneys convert it to hormone calcitriol  Calcitriol is used to help absorb calcium and phosphorous by small intestine.

Cholecalciferol/Vitamin D3 can be absorbed from food…egg yolk, fish oil, fortified milk.

Lack of enough sunlight exposure or Vitamin D3(cholecalciferol) in diet –abnormal bone development maintenance & growth

 Rickets in children…weak bones, bowed legs (bending of bones)  Osteomalacia in adults Accessory Structures

Structures associated with skin…hair, glands and nails.

Hair, glands and nails may be located in dermis but derived from epidermis….referred to as epidermal derivatives.

Keratin may be loosely arranged (soft keratin in skin epidermis). Keratin may be tightly packed (hard keratin in nails and hair). Accessory structure-Hair

Non-living structures produced in organs called hair follicles Anatomy: Shaft – part that projects beyond the skin. Root – part that is embedded in the skin. Bulb – swollen base of the hair. Hair/dermal papilla-contains blood vessels and nerves Arrector pili: a band of smooth muscle that connects hair follicle to the epidermis, when contracts  lifts hair and follicle  goose bumps  hair erect

Types of hair: Lanugo- fine hair of fetus  shed soon after birth. Vellus hair- fine hair all over the body. Terminal hair- thicker hair on head, eyelash, eyebrow, nose, axillary, pubis. Accessory structure-Hair

Alopecia: Partial or complete loss of hair due to hormonal changes or skin disease.

Hirsutism: Excessive hair due to hypersecretion of androgens. More obvious in women and children. Accessory structure- Glands

Glands: exocrine glands that discharge their secretions to outside through a duct. 1) Sudoriferous glands 2) Mammary glands 3) Sebaceous glands 4) Ceruminous glands Accessory structure- Glands

Accessory Structures

Hair shaft 1) Sudoriferous (sweat) glands: Pore of sweat Unevenly distributed….more in thick skin. gland duct Gland is located in dermis  duct opens through a pore on skin surface. Sebaceous gland Secrete sweat….perspiration.

Insensible perspiration: sweating you are Sweat gland duct unaware of….through stratum corneum or Hair follicle damage of the skin.

Sensible perspiration: sweating you Sweat gland notice….normal through sweat glands…cools down the body-regulates body temperature.

Sweat also gets rid of water, electrolytes & metabolic waste

Diaphoresis: excessive sweating due to exercise, heat or nervousness…really drips! Accessory structure- Glands

2) Mammary glands: - Modified sudoriferous gland. - Located in thoracic region of males and females. - Has abundant adipose tissue associated with it. - Produce nutrition-rich fluid….milk. Accessory structure- Glands

3) Ceruminous (wax) glands: - Modified sudoriferous gland. - Located in the skin lining the external ear canal –Its waxy secretion combines with oil of sebaceous gland  cerumen (ear wax).

Function: Ear protection Prevent entrance of water, foreign particles and insects  prevent damage of the eardrum. Accessory structure- Glands

Accessory Structures 3) Sebaceous (oil) glands:

Hair shaft Mostly associated with hair follicles  open Pore of sweat into the neck of the follicles-Secrete oily gland duct substance – sebum.

Sebaceous gland Keeps skin soft, prevents excessive and heat loss

Sweat gland duct Acne: inflammation of sebaceous gland. Hair follicle Sebaceous follicles get colonized by certain bacteria  cyst formation – cystic acne  permanent scarring.

Sweat gland Accessory structure- Nails

Nails: Hard, keratinized epidermis that projects out. Can be divide into- Free edge Nail body Nail root

Function: Help in grasping and manipulating small objects. Protect fingertips. Thin vs. Thick Skin

Thin skin: Thick skin: 1) Thin, smooth and soft. 1) Thick, rough and harder. Covers most of the body. Covers palms and soles. Composed of 4 layered epidermis: Composed of 5 layered epidermis: Stratum corneum Stratum corneum Stratum granulosum Stratum lucidum Stratum spinosum Stratum granulosum Stratum basale Stratum spinosum Stratum basale 2) Stratum corneum is thinner. 2) Stratum corneum is thicker. 3) Thinner dermis. 3) Thicker dermis. 4) Hair present. 4) No hair associated with it. 5) Sebaceous (oil) glands present. 5) No sebaceous (oil) glands present. 6) Fewer sudoriferous (sweat) glands  6) More sudoriferous (sweat) glands  more lesser sweating. sweating. 7) Fewer sensory receptors. 7) More sensory receptors. Skin Wound Healing There are two types of skin injuries:

1. Superficial wound: Abrasion or burn that is restricted to epidermis…although the center may extend to the dermis.

2. Deep wound: Injury that goes through the epidermis and dermis….lacerations and surgical incisions. Skin Wound Healing – Superficial Wound Healing

1. Superficial wound: Abrasion or burn that is restricted to epidermis…although the center may extend to the dermis. Stratum basale cells divide  migrate across the wound  new cells fill the gap by moving upwards and form new strata  epidermis is healed. Takes about 24-48 hours. Skin Wound Healing – Deep Wound Healing

2. Deep wound: This type of healing is more complex and can take several days. Process is divided into 4 phases: A. Inflammatory phase B. Migratory phase C. Proliferative phase D. Maturation/Scarring phase

A. Inflammatory phase B. Migratory phase

Scab is a blood clot Stratum germinativum is a synonym of stratum basale Injury site Skin Wound Healing – Deep Wound Healing

C. Proliferative phase D. Maturation/Scarring phase

scab

migratory epithelial cells Burns

Can be due to exposure to sun, heat, electricity, radioactivity or chemicals. Causes denaturation of proteins  death of the cells.

Can affect body functions in multiple ways: Lack of skin:- 1) Easy evaporation of water

2) Dehydration  reduced urine production  kidneys may shut down  build up of toxic waste.

3) Drop in body temperature

4) Infections

5) Reduced blood volume  reduced blood pressure Burns First degree burn: restricted to epidermis….as in sunburn. Mild pain, erythema, slight edema, flaking/peeling of the skin. Heals in 2-3 days.

Second degree burn: involves entire epidermis and part of dermis. Loss of some skin functions….hair follicles, glands are not lost. Erythema, blister formation, marked edema and pain. Heals in 7-10 days.

Third degree burn: involves entire epidermis and dermis, and extend into hyodermis. Appears marble-white, not as painful (nerve ending destroyed), may require grafting.

1st degree 2nd degree 3rd degree Skin Grafting

If skin is lost over a large surface area  it cannot regenerate on its own. Skin graft is done using the skin from the patient, another human being, another animal or one generated in the lab. Without a successful graft, the patient will experience infections, dehydration and temperature fluctuations. Different types of grafts: Autograft- skin taken from the same person…from one area of the body to another. Isograft- skin taken from identical twin. Homograft- skin taken from same species…another human being….usually cadaver, foreskin of circumcised infant. Heterograft- temporary graft using skin from another animal. Synthetic skin- a temporary plastic covering generated in a lab. Best results are from autograft or isograft. Other sources can cause substantial immune rejection. Skin Cancer

Skin cancer: Most often caused by overexposure to sunlight or chemicals. Type depends on the cell type that begins the process: Carcinoma- derived from epidermal cells. Melanoma- derived from melanocytes…..often a dark tumor. Risk factors: Skin type – lighter skin has greater incidence. Sun Exposure – greater in areas with longer sun hours or at higher altitudes. Family history – could be genetic. Age – older individuals have higher incidence. Immunologic status – individuals on immunosuppressive or chemotherapy drugs have greater incidence. Sun tanning  increases the chance. PABA in sun-protection  lowers the chance. Skin Aging

With age, following changes take place in the integumentary system: Fibroblasts decrease  Decrease in collagen fibers, stiffening and breaking  skin becomes loose. Decrease in elastic fibers  skin becomes wrinkled and looses elasticity. Decrease in number of WBCs  more infections. Decrease in subcutaneous fat  skin becomes thinner. Decrease in melanocyte activity  patchy skin, loss of color in hair. Increased incidence of skin cancer, itching, bedsores. Decreased sebum secretion  skin becomes dried and cracks  infections.