The Integumentary System PDF

The Integumentary System Objective The Integumentary System Integument is skin Skin and its appendages make up the integumentary system A fatty layer (hypodermis) lies deep to it Two distinct regions ◻ Epidermis ◻ Dermis  STRUCTURE OF THE SKIN epidermis...

The Integumentary System Objective The Integumentary System Integument is skin Skin and its appendages make up the integumentary system A fatty layer (hypodermis) lies deep to it Two distinct regions ◻ Epidermis ◻ Dermis  STRUCTURE OF THE SKIN epidermis dermis hypodermis - Derived from -relatively dense and -subcutaneous layer rich ectodermal germ layer of vascular connective in fat and areolar tissue the embryo tissue - Fully formed by the 17th -2 layers -varies with nutrition week of gestation a.Thin papillary - Thicker in obese people b.Reticular layer -cell type include keratin, melanin and langerhans - outer/ thinner - Inner /thicker 5 strata Functions of skin Protection ◻ Cushions and insulates and is waterproof ◻ Protects from chemicals, heat, cold, bacteria ◻ Screens UV Synthesizes vitamin D with UV Regulates body heat Prevents unnecessary water loss Sensory reception (nerve endings)  Functions of the skin 1. Protection 📫Physical barrier to microorganisms 📫Barrier to chemical hazards 📫Reduce potential for chemical trauma 📫Prevent dehydration 📫Protect from excess UV exposure 📫Surface film- a emulsified protection barrier formed when mixing of residues and secretions of sweat and sebaceous glands sloughed epithelial cells from skin surface. This film is anti-bacterial activity, lubrication, causes movement to occur without injury, it’s a buffer for caustic irritants and blocked toxic agents.  2. Sensation 📫Sense organs 📫Have somatic sensory receptors which detect stimuli of pressure, touch, temperature and pain 3. Excretion 📫Regulate the volume and chemical content of sweat 📫Influence total fluid volume and amount of waste products such as uric acid, ammonia and urea 📫The function of the sweat glands is to keep the body temperature constant by the evaporation of water. (explain how the sweat glands function) 📫Microscopic bacteria act on the water to produce a bad odor 4. Vitamin D production 📫Exposure of skin to UV light covert dehydrocholesterol to calciferol – a precursor to vit. D. Calciferol is transported to the liver and kidney by the blood where vitamin D is produced 5. Immunity 6. temperature control  Skin classification based on epidermal layer 1. Thin skin 📫 Covers most of the body 📫 Less number of cell layers than in thick skin 📫 One or more strata may be entirely absent 📫 Raised parallel ridges not present in the dermis 2. Thick skin 📫 Covers palm of hands and finger tis, sole of feet and other body area subject to friction 📫 Each of the 5 strata of the epidermis are present and are generally several cell layers thick 📫 Includes- stratum corneum (horney layer), stratum lucidum (clear layer), stratum granulosum (granular layer) , stratum spinosum (spiny layer) and stratum basale (base layer) Epidermis Keratinized stratified squamous epithelium Four types of cells ◻ Keratinocytes – deepest, produce keratin (tough fibrous protein) - Comprised over 90% of the epidermal cells and form principal structural element of the outer skin. ◻ Melanocytes - make dark skin pigment melanin - Contributes to skin color and serve to filter ultraviolet light - Comprise over 5% of the epidermal cells ◻ Merkel cells(tactile) – associated with sensory nerve endings ◻ Langerhans cells(epidermal dendritic) – macrophage-like dendritic cells - Plays a limited rile in immunological reactions that affect the skin and may serve as a defense mechanism for the body. - Originates in the bone marrow but migrate to deep cell layers in the epidermis early in life - Function to trigger immune reaction in pathological conditions  Layers (from superficial to Deep) ◻ Stratum corneum – horny layer 📫 Composed of very thin squamous cells that are dead at the skin surface and are continually replace 📫 Cytoplasm replaced by keratin 📫 Layer strengthen by desmosomes which hold adjacent keratinocytes together Function: As a barrier to water loss and many environmental threats ranging from microorganisms and harmful chemical to physical trauma. Note: If the layer is damage, the effectiveness of the skin as a protective layer is greatly reduced. * Hyperkeratosis  Stratum Lucidum and Stratun Granulosum Stratum Lucidum 📫Clear packed, no nuclei 📫Filled with eleidin, a soft jelly substance which eventually transforms to keratin 📫Function to block water penetration or loss 📫Absent in thin skin Stratum Granulosum 📫Process of keratinization begins here 📫Cells are arranged in a sheet of 2-4 layers and are filled with intensely staining granules called KERATOHYALIN required for keratin formation 📫May be missing in some regions of thin skin  Stratum Spinosum and Stratum Basale Stratum Spinosum 📫Form from 8-10 layers of irregularly shaped cells with prominent intercellular demosomes. 📫Cells are rich in RNA and therefore well equipped to initiate protein synthesis required for production of keratin Stratum Basale 📫Single layer of columnar cells 📫Cells undergo mitosis 📫Migrate to other layers until they are shed from the skin Epithelium: layers (on left) and cell types (on right)  Epidermal growth and repair 1. Turn over or generation time- refers to the time required for epidermal cells to form the stratum Basale and migrate to the skin surface- about 35 days. 2. Shorten repair time will increase thickness of stratum corneum and result in callus formation. 3. Normally 10-12% of all cells in the stratum basale enter mitosis daily. 4. Each group of 10 basal cells in mitosis with their vertical column of migrating keratinocytes is called an epidermal proliferating unit or CPU Remember… Four basic types of tissue ◻ Epithelium – epidermis just discussed ◻ Connective tissue - dermis ◻ Muscle tissue ◻ Nervous tissue  Dermis Strong, flexible connective tissue Much thicker than the epidermis and may exceed 4mm in the sole and palms Thinnest on the eyelids and penis where it is seldom 0.5mm Cells: fibroblasts, macrophages, mast cells, WBCs Fiber types: collagen, elastic, reticular Rich supply of nerves and vessels Critical role in protection, reservoir storage of water and important electrolytes and temperature regulation Consist of specialized network of nerve and nerve endings called SOMATIC SENSORY RECEPTORS which serve to process sensory information. Two layers (see next slides) ◻ Papillary – areolar connective tissue; includes dermal papillae ◻ Reticular – “reticulum” (network) of collagen and reticular fibers *Dermis layers *Dermal papillae * *  Papillary and Reticular layer 1. Papillary - Comprise essentially of loose connective tissue elements and a fine network of thin collagenous and elastic fibers. 📫Composed of dermal papillae that projects into the epidermis 📫Contain the dermal –epidermal junction 📫Forms a unique pattern that gives individual finger prints 2. Reticular 📫Contain dense, under lacing white collagenous fibers and elastic fibers to make the skin tough yet stretchable. 📫When process from animal skin produces leather  Dermal Growth and Repair 1. The dermis does not continually shed and regenerate itself as the epidermis 2. During wound healing, the fibroblast begin forming an unusually dense mass of raw connective fibers. If not replaced by normal tissue it forms a scar. 3. Langer’s line (cleavage lines)- patterns formed from the collagenous fibers of the reticular layers of the skin.  Skin Color 📫 Determined by the quality of melanin 📫 Melanin is formed in the melanocytes from amino acids tyrosine with the help of the enzyme tyrosinase. 📫 Lack of melanin results in ALBINISM 📫 The process is regulated by: 1. Tyrosinase 2. Exposure to sunlight 3. Hormones MSH- melanocyte stimulating hormone and ACTH (adrenocorticotrophic hormone) produced by the pituitary gland 4. Increase age * Carotene also contributes to skin color Epidermis and dermis of (a) thick skin and (b) thin skin (which one makes the difference?) Fingerprints, palmprints, footprints Dermal papillae lie atop dermal ridges Elevate the overlying epidermis into epidermal ridges Are “sweat films” because of sweat pores Genetically determined Flexion creases The dermis is the receptive Deep dermis, from continual folding site for the pigment of tattoos Fibers Collagen: strength and resilience Elastic fibers: stretch-recoil ◻ Striae: stretch marks Tension lines (or lines of cleavage) ◻ The direction the bundles of fibers are directed Hypodermis “Hypodermis” (Gk) = below the skin “Subcutaneous” (Latin) = below the skin Also called “superficial fascia” “fascia” (Latin) =band; in anatomy: sheet of connective tissue Fatty tissue which stores fat and anchors skin (areolar tissue and adipose cells) Different patterns of accumulation (male/female) Skin color Three skin pigments ◻ Melanin: the most important ◻ Carotene: from carrots and yellow vegies ◻ Hemoglobin: the pink of light skin Melanin in granules passes from melanocytes (same number in all races) to keratinocytes in stratum basale ◻ Digested by lysosomes ◻ Variations in color ◻ Protection from UV light vs vitamin D? Skin appendages Derived from epidermis but extend into dermis Include ◻ Hair and hair follicles ◻ Sebaceous (oil) glands ◻ Sweat (sudoiferous) glands ◻ Nails  Nails Consist of epidermal cells converted to hard keratin Development begins about week 10 and the nails of the toe develops before the nails of the fingers Corresponds to hooves and claws Function of the nails is to grasp, manipulate and protection from trauma Grows from nail matrix  Structure of the Nail 1. Nail body- visible part of each nail 2. Root- part of nail groove hidden by folds of skin cuticle 3. Lunula- moon-shape white area nearest root 4. Nail bed- layer of the epithelium under nail body, contains abundant amount of blood vessels * Nails grow by mitosis of cells in the stratum  HAIR 📫 It is an assessory organ 📫 It is found all over the body except on lips, palm of hands and soles of feet and a few other small areas. 📫 The development of the hair begins in the 3rd fetal month with the development of hair follicles. At the 5th month fine soft hair called LANUGO covers the body but sheds before birth. At 5-6th month the terminal hair merges but it is the same follicle that develops at the 3rd fetal month. 📫 At puberty, coarse pubic and axillary hair develops. Hair and hair follicles: complex Derived from epidermis and dermis Everywhere but palms, soles, nipples, parts of genitalia *“arrector pili” is smooth muscle * Hair bulb: epithelial cells surrounding papilla Hair papilla is connective tissue________________  Functions of hair ◻ Warmth – less in man than other mammals ◻ Sense light touch of the skin ◻ Protection - scalp Parts ◻ Root imbedded in skin ◻ Shaft projecting above skin surface Make up of hair – hard keratin Three concentric layers ◻ Medulla (core) ◻ Cortex (surrounds medulla) ◻ Cuticle (single layers, overlapping)  Types of hair ◻ Vellus: fine, short hairs ◻ Intermediate hairs ◻ Terminal: longer, courser hair Hair growth: averages 2 mm/week ◻ Active: growing ◻ Resting phase then shed Hair loss ◻ Thinning – age related ◻ Male pattern baldness Hair color ◻ Amount of melanin for black or brown; distinct form of melanin for red ◻ White: decreased melanin and air bubbles in the medulla ◻ Genetically determined though influenced by hormones and environment  Types of sweat glands Eccrine or merocrine ◻ Most numerous ◻ True sweat: 99% water, some salts, traces of waste ◻ Open through pores Apocrine ◻ Axillary, anal and genital areas only ◻ Ducts open into hair follices ◻ The organic molecules in it decompose with time - odor Modified apocrine glands ◻ Ceruminous – secrete earwax ◻ Mammary – secrete milk  Sweat glands Entire skin surface except nipples and part of external genitalia Prevent overheating 500 cc to 12 l/day! (is mostly water) Humans most efficient (only mammals have) Produced in response to stress as well as heat  SWEAT GLANDS(sudoriferous) 1. Sudoriferous glands (sweat glands) 📫2 types: 1. Eccrine(merocrine) glands – numerous, distributed on palm and sole of feet and function in secretion and temperature control. 2. Apocrine – larger than eccrine, distributed in axillary and genial areas, contain fat and proteins, secretion is odourless until organic decomposition occurs, activates during stress and pain, increase during foreplay and it is secreted during puberty and triggered by the production of androgens. 2. Sebaceous gland- attached to hair follicles, made of epithelial cells and function in the production of sebum 3. Cerminous glands- modified apocrine glands that function in the production of cenimen/wax to protect the ear Sebaceous (oil) glands Entire body except palms and soles Produce sebum by holocrine secretion Oils and lubricates Disorders of the integumentary system Burns ◻ Threat to life Catastrophic loss of body fluids Dehydration and fatal circulatory shock Infection ◻ Types First degree – superficial, epidermis and hair burns off, minor pain, healing in a few days and there is no scaring, no blisters but some redness and surface peeling. Second degree – deep partial thickness, epidermis and upper dermis is burnt, severe pain, healing depends on cells that survive, scaring, blister with swelling and edema Third degree - full thickness, total destruction of both epidermis and upper dermal layers, tissue death extend below level of hair follicles and sweat gland, no immediate pain since nerve endings are destroyed, scaring occurs and may require grafting Burns First-degree (epidermis only; redness) Second-degree (epidermis and dermis, with blistering) Third-degree (full thickness, destroying epidermis, dermis, often part of hypodermis)  Estimate by “rule of 9’s” Critical burns Over 10% of the body has third-degree burns 25 % of the body has second-degree burns Third-degree burns on face, hands, or feet Tumors of the skin Benign, e.g. warts Cancer – associated with UV exposure (also skin aging) ◻ Aktinic keratosis - premalignant ◻ Basal cell - cells of stratum basale ◻ Squamous cell - keratinocytes ◻ Melanoma – melanocytes: most dangerous; recognition: A - Asymmetry B - Border irregularity C - Colors D - Diameter larger than 6 mm  Skin Cancer Sqaumous cell carcinoma Basal cell carcinoma Melanoma  1. List the 5 layers making up the epidermis beginning at the basement membrane and travelling to the free surface. 2. The primary pigments contained in the epidermis are _____and ______. 3. The major component of the dermis are the ____and _______. 4. The assessor structures of the integument includes ___________. 5. Two major exocrine gland in the skin are ____and _____. 6. In some cultures, some women must be covered completely, except for their eyes, when they go outside. These women exhibit incidence of problems with their bones. Why? 7. What are the functions of sebaceous secretions? 8. Deodorants are used to mask the effects of secretions from which skin gland? 9. Which type of skin gland is most affected by the hormones that occur during puberty? 10. Why can skin regenerate effectively even after considerable damage may have occurred? 11. A new mother notices that her 6 month old child has a yellow orange complexion. Fearful that the child may have jaundice she takes him to the paediatrician. After examining the child, the paediatrician declares him perfectly healthy and advises the mother to watch the child’s diet. Why?