TOPIC 2 - THE INTEGUMENTARY SYSTEM.pptx

TOPIC 2 INTEGUMENT ARY SYSTEM Learning outcomes: At the end of this topic, students should be able to:  Describe the structure of the skin.  Describe the general functions of the integumentary system.  Describe the main structural features of the epidermis and explain their functional...

TOPIC 2 INTEGUMENT ARY SYSTEM Learning outcomes: At the end of this topic, students should be able to:  Describe the structure of the skin.  Describe the general functions of the integumentary system.  Describe the main structural features of the epidermis and explain their functional significance.  Describehow the integumentary system helps regulate body temperature.  Discuss the functions of the skin's accessory structures.  Introduction  The integumentary system consists of the skin, hair and nails.  It serves both as a covering and as a protection for the body.  The system functions in:  protection  the regulation of body temperature  the excretion of waste materials  the synthesis of vitamin D3 with the help of sunrays  thereception of various stimuli perceived as pain, pressure and temperature.  Skin  The largest organ in the body.  Occupying almost 2m² of surface area, thickens of 2mm.  It is completely covers the body.  Skin has 3 main parts:  Epidermis  Dermis  Hypodermis / subcutaneous tissue  Epidermis  Is the outer layer of the skin.  Made of stratified squamous epithelium.  Function – to protects the body from friction and water loss.  Has no blood vessels or nerve endings in the epidermis – can easily rub off the dead skin without bleeding.  Complete replacement of the epidermis takes about a month  Cont..  Epidermis contains of 5 strata (layers) of cells: i. Stratum corneum ii. Stratum lucidum iii. Stratum granulosum iv. Stratum spinosum v. Stratum basale  Cont..  Stratum corneum is the outermost layers of the epidermis, dead, flat, keratinized and thicker layer.  Contain soft keratin (protein that helps keep the skin hydrated & elastic).  Stratum lucidum is a thin, clear layer of dead skin cells. Found beneath the stratum corneum of thick skin. At this layer keratin production increase.  As a protective shield against ultraviolet-ray damage (sunburn).  Stratum granulosum lies just below stratum lucidum.  Contain granules of keratohyaline – undergo a process of keratinization, associated with the dying process of cells.  Cont..  Stratum spinosum located next down to stratum ganulosum.  The thickest stratum, initiates keratinization (production of keratin). At this layer keratinocytes are joined by tight intercellular junctions called desmosomes.  Stratum basale rests on the basement membrane, and it is last layers of epidermis next to stratum spinosum.  Consists of a single layer of tall, simple cuboidal epithelial cells. Scattered among these are the melanocytes and tactile cells.  Stratum basale together with stratum spinosum constitute stratum germinativum – generate new cells  Cont..  Epidermis layers contain 4 types of cells:  Keratinocytes produce keratin (a protein) – gives skin strength, flexibility and waterproof surface.  Melanocytes produces melanin (dark pigment) – skin color  Merkel’s cells – light touch / pressure reception  Langerhans’ cells – help the immune system  Dermis A layer of skin beneath the epidermis.  Consists of 3 types of strong, flexible of connective tissue / types of fibers: i. Collagen fibers ii. Reticular fibers iii. Elastic fibers  Most part of the skin is composed of dermis.  Cont..  The cells of dermis are mostly fibroblasts (cell that form connective tissue), fat cells & macrophages.  Itcontains the hair follicles, sweat glands, sebaceous glands, apocrine glands, blood vessels & nerve endings.  Nerve - provide the sense of touch and heat.  Bloodvessels – provide nourishment and waste removal. SKIN ANATOMY  Structure of Dermis  It has two layers: - The papillary layer - The reticular layer  Papillary layer  Next to stratum basale of the epidermis.  Contain loose connective tissue with the bundles of collagenous fibers.  Also contains loose capillaries that nourish the epidermis.  Ithas the fingerlike projections called papillae, that extend toward the epidermis.  Have special nerve endings that serve as touch receptors (Meissner’s corpuscles). A double row of papillae in finger pads produces the friction ridges, occur in patterns (fingerprint) on fingertips -> genetically determined, different in individual, making it possible to use fingerprints or footprints as a means of identification.  Reticular Layer  It lies deep in the papillary region and is usually much thicker.  It is composed of dense irregular connective tissue.  Contains Pacinian corpuscles, sensory receptors for deep pressure.  This layer contains:  Blood vessels.  Lymph vessels.  Sensory nerve endings.  Sebaceous glands.  Sweat glands.  Hair.  Hypodermis  Known as subcutaneous layer.  It is found beneath the dermis.  Composed of loose, fibrous connective tissue such as adipose tissue.  Itis richly supplied with lymphatic, blood vessels and nerves.  Withinthe hypodermis – coiled ducts of sweat glands and base of hair follicles. Arrector pili muscle – contracts to cause the follicle to stand upright.  Functions of Skin 1) Protection: against harmful microorganisms, foreign material and it prevents excessive loss of body fluid. 2) Temperature regulation: with the sweat, heat leaves the body. 3) Excretion: Small amount of waste products from the body such as urea. 4) Synthesis: by the action of UV. Vitamin D is synthesized in the skin. Vit D necessary for calcium absorption. 5) Sensory reception: it contains sensory receptors of heat, cold, touch, pressure and pain.  Color of the Skin  Skin’s color is determined by 3 factors: 1) The presence of melanin – a dark pigment produced by specialized cell called melanocyte. 2) The accumulation of yellow pigment carotene. 3) The color of blood reflected through the epidermis.  The main function of melanin is to screen out excessive ultraviolet rays.  All races have some melanin in their skin, the darker races have slightly more melanocyte.  The person who is genetically unable to produce any melanin is an albino.  Glands of the Skin Sudoriferous/sweat glands.  It composed of epithelial cells.  They are distributed over nearly the entire body surface, eg: palms, soles, axilla & groin.  The bodies of the glands lie coiled in the subcutaneous tissue.  Types:Eccrine and Apocrine glands.  Eccrine glands  Small, simple coiled tubular glands distributed over nearly the entire body.  They are absent over nail beds, margins of lips of vulva and tips of penis but numerous over the palms and soles.  The sweat they secrete is colorless, aqueous fluid containing neutral fats, albumin, urea, lactic acids and sodium chloride.  Its excretion helps body temperature to be regulated.  Apocrine glands  Found at the armpits, in the dark region around nipples, the outer lips of the vulva and genital regions.  They are larger and deeply situated than eccrine sweat glands.  This glands becomes active at puberty.  They respond to stress including sexual activity.  The female breasts have apocrine glands that become adapted to secrete and release milk instead of sweat. Sebaceous (oil) glands  The glands found in the dermis.  Their main functions are lubrication and protection.  They are connected to hair follicles and secret oily secretion called sebum.  Cont..  It is a semifluid substances composed of entirely lipids.  Its functions as an emollient (skin softening) and as a protective agent against bacteria and fungi.  Found all over the body except in the palms and soles.  Sebum keeps hair moist and prevents skin from drying.  During puberty, increased sex hormone levels in the blood may produce excessive sebum. Over secretion of sebum will plugs the gland and hair follicle, producing a skin disorder called acne.   Sebum a semifluid substance composed almost entirely of lipid. About 60% of sebum consists of glycerides and fatty acid. Function: lubrication & protection. Keep the hair soft A protective agent against & bacteria & fungi. gives a shinny appearance Prevents drying & cracking of skin especially exposure to heat & sunshine. 32  When sebaceous glands become inflamed & accumulate sebum. If plugging The gland opening not relieved becomes plugged Sebaceous Pimples Blackhead Cyst Hormonal changes during puberty  Hair  Composed of keratinized threads of cells, which develops from the epidermis.  Because it arises from the skin, it is considered an appendage of the skin.  Covers the entire body except the palms, soles, lips, tips of penis, inner lips of vulva and nipples.  Function of Hair  Scalp hair plays an important role in preventing trauma to the skull.  Eyelashes and eyebrows keep dust, dirt & screen against foreign particles.  In the nostrils, hair trap dust particles in the inhaled air.  Protects openings from foreign particles.  Structure of Hair  Hair has two parts, the shaft (the part above the skin) and the root (embedded in the skin).  It consists of epithelial cells arranged in three layer from the hair shaft. Medulla  composed of soft keratin.  forms the central core of the hair. Cortex  composed of hard keratin.  the thickest layer of hair.  pigment in the cortex gives hair its color. Cuticle  composed of hard keratin.  made up of thin squamous cells. Hair shaft - the portion of the hair that protrudes from the skin. Root - embedded beneath the skin. The bulb - at the lower portion of the root, located in the hypodermis.  Cont..  Hairfollicles are structures within your skin that grow your hair.  The hair is formed by the multiplication of cells  Asthe new hair start to grow, pushing the old hair to be shed. Hair follicle consists of three sheath: An inner epithelial root sheath An outer epithelial root sheath A connective tissue sheath.  The Arrector Pili A little bundles of smooth muscle fibers attached to the hair follicles.  When it contracts, it pulls the follicle and its hair to stand erect and raises the skin around the hair, producing goose bump.  The contraction of the muscle is involuntary.  Stimulateby stresses such as cold, fear etc., and thus cause muscle contraction. Structure of Hair  Nails  Made of hard keratin.  They appear pink, because the nail is translucent, allowing the red color of the vascular tissue underneath to show through.  Cont..  The proximal part of nail is lunula.  White in color because of the capillaries underneath are covered by thick epithelium.  Nail body is the exposed part.  Nail root is hidden under the skin.  Free edge of nail– overhangs the tip of the fingers  Hyponychium is the thick skin under your nail tip – secures nail to the fingertip.  Nail bed is the nail rests on an epithelial layer of skin.  Nail matrix is the thicker layer of skin beneath the nail root – generate new cell  Cont..  Eponychium is the thin layers of epidermis called (cuticle) originally cover the growing nail.  Fingernails grow faster than toenails.  Both fingernails & toenails grow faster in warm weather than in cold.  Functions of the nails: i. It protect ours fingers & toes ii. It allow us to pick up and grasp objects iii. We use them to scratch  References  Tortora, G.J & Derrickson, B. (2017) Essentials of Anatomy and Physiology. (15th ed), NJ. John Wiley & Son.  Waugh, A & Grant, A. (2018) Ross and Wilson Anatomy and Physiology in Health and Illness (13th ed), Philadelphia. Elsevier.