Integumentary System PDF

The Integumentary System - largest "organ" of the body - skin, hair, glands, nails, sensory receptors, etc. - Functions - forms a protective barrier, starts Vitamin D production, Sensory, Thermoregulation, social Copyright © 2002 Michael H. Mitchell – A...

The Integumentary System - largest "organ" of the body - skin, hair, glands, nails, sensory receptors, etc. - Functions - forms a protective barrier, starts Vitamin D production, Sensory, Thermoregulation, social Copyright © 2002 Michael H. Mitchell – All Rights Reserved Figure 5.2 Layers of Skin The skin is composed of two main layers: the epidermis, made of closely packed epithelial cells, and the dermis, made of dense, irregular connective tissue that houses blood vessels, hair follicles, sweat glands, and other structures. Beneath the dermis lies the hypodermis, which is composed mainly of loose connective and fatty tissues. From Openstax free textbook, Human Anatomy and Physiology. Figure 5.1 Epidermis Papillary Layer of Dermis Dermis Reticular Layer of Dermis Hypodermis (g) Stratum Corneum (a) Stratum Lucidum (b) Stratum Granulosum (c ) Stratum Spinosum (d) Stratum Basale or Stratum Germinat  Dermal Papillae (f) Eccrine Sudoriferous Gland Duct (j) Capillary (r) Pore – eccrine sudoriferous gland Stratum Granulosum (c ) Stratum Spinosum (d) Dermal Papillae (f) (pl, Papilla is singular) Sebaceous Gland(n & o) Eccrine Sudoriferous Gland (h) Artery (p) Vein (q) Eccrine Sudoriferous Gland (h) Apocrine Sudoriferous Gland (l) Meissner’s Corpuscle (w) v Arrector Pili Muscle (x) Hair Follicle (A) Sensory Neuron (t) Motor Neuron (s) Motor Neuron (s) Sensory Neuron (t) Laminar Corpuscle or Pacinian Corpuscle (u)  Hair Shaft (J) Sebaceous Gland(n & o) Connective Tissue Sheath (C ) Glassy Membrane (D) External Epithelial Root Sheath (E) Internal Epithelial Root Sheath (F) Cuticle layer (G) Cortex layer (H) Medulla layer (I) Hair Papilla (K) Lab Model - Photo by M. H. Mitchell  Layers of Skin 1. Epidermis - outermost layer = keratinized stratified squamous ET - Keratinocytes - most abundant cells of epidermis - produce the protective protein Keratin – a protein found in skin, hair, and nails - waterproofs and hardens – protects. - Melanocytes – approx 10% of stratum basale cell - repair UVB damage to DNA - produce the brown pigment Melanin which is transferred to Keratinocytes. - Keratinocytes make a "cap" or shield of melanin around the "sunny" side” of the nucleus to protect it from the damaging effects of ultra-violet light (causes Thymine to bind to Thymine rather than Adenine resulting in Thymine Dimers which (if in the appropriate gene) is one of the causes of skin cancer - UV light also causes elastin fibers to clump producing "leathery" skin and reduces folate (folic acid) reserves which are used in the production of DNA - remember, folic acid is especially important in reducing the risks of neural tube defects - Dendritic Cells = Langerhans' Cells - phagocytes of the immune system that ingest foreign substances - Merkel Copyright Cells +H.Sensory © 2002 Michael Mitchell –Nerve Ending All Rights = Merkel Disc = touch receptor Reserved  Layers of Skin Basement membrane that binds the basal surface of the epithelial cell to the underlying tissues - composed of glycoproteins - 2 layers of basement membrane 1. Basal Lamina - secreted by epithelial cells 2. Reticular Lamina - secreted by underlying connective tissue cellsses Thymine to bind to Thymine rather than Adenine resulting in Copyright © 2002 Michael H. Mitchell – All Rights Reserved  - Layers of Epidermis - stratified squamous epithelium a. Stratum Basale aka Stratum Germinativum because it contains mitotically active cells - i.e. the cells are actively dividing - Cuboidal cells w/ Basement Membrane - Keratinocytes & Melanocyes are produced here - Merkel Cells - a type of tactile cell (Tactile = touch) - deepest or innermost layer of the epidermis b. Stratum Spinosum - many layers of keratinocytes – about 10 -30 cells thick - second from the deepest layer of the epidermis c. Stratum Granulosum - 3-5 layers - 3rd deepest layer of epidermis - granular appearance due to "keratin" and glycolipid granules - cells begin to die and flatten d. Stratum Lucidum - very thin, translucent layer - in thick skin only - only found in the palms & soles e. Stratum Corneum - up to 10-30 layers in some areas - very thick, protective produces Dandruff, Calluses, etc. - epithelial cells last about 4-8 weeks then they are exfoliated - Vernix Caseosa - a layer of sebaceous secretions (and dead cells, etc) that protects the fetal skin from the amniotic fluid Figure 5.5 Layers of the Epidermis The epidermis of thick skin has five layers: stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum. From Openstax free textbook, Human Anatomy and Physiology. - Layers of Dermis - tatoos must reach this layer or be lost with the shedding eipidermal cells. a. Papillary Layer - only 1/5 or 20% of the thickness of dermis - Dermal Papillae upward, wavy, finger-like projections of dermis into the epidermis - Dermal Ridges - thick mounds of the dermis forcing the epidermis up - These make finger prints - contains capillaries, free nerve endings (for pain) - Meissner’s corpuscles - Tactile corpuscles - Layers of Dermis b. Reticular Layer – deepest & thickest 4/5 or 80% of dermis - Striae - stretch marks due to torn collagen fibers in dermis - tattoo must reach this layer otherwise lost with epithelial cells - Leather & suede are produced from this layer in cattle etc. – epidermis & papillary layer removed - composed of of dense irregular CT - Lamellar corpuscles (Pacinian corpuscles) – sense vibration & deep pressure - Arrector pili muscle* - base of hair shaft – make hairs stand up (Goose Bumps or Goose Flesh) - Eccrine sudoriferous gland* - sweat glands – evaporative cooling - Apocrine sudoriferous gland – base of axillary and pubic hair follicles - possible scent glands ? - activate at puberty - Sebaceous gland* – produce sebum – oil – waterproofs - Sensory nerve fibers – nerve impulses send sensations of heat & pain to brain - Motor nerve fibers – from CNS to effectoers - Free nerve endings – nerve impulses send pain sensations of pain to brain Hypodermis, or superficial fascia (composed of adipose CT) (deep to the integument – not part of it) Figure 5.7 Layers of the Dermis This stained slide shows the two components of the dermis—the papillary layer and the reticular layer. Both are made of connective tissue with fibers of collagen extending from one to the other, making the border between the two somewhat indistinct. The dermal papillae extending into the epidermis belong to the papillary layer, whereas the dense collagen fiber bundles below belong to the reticular layer. LM × 10. (credit: modification of work by “kilbad”/Wikimedia Commons) From Openstax free textbook, Human Anatomy and Physiology.  Skin Color due to: - Melanin - gives a brown color to skin - Hemoglobin - gives a red/pinkish color to skin - Carotene - gives a yellow-orange color to skin - Cyanosis - a bluish color of the skin due to reduced oxygen content - Erythema - a reddening of the skin due to vasodilation of small vessels in skin - Pallor - the skin becomes more pale due to a reduction in blood flow  - Sensory Receptors of Skin - 1. Meissner's Corpuscles - in dermal papillae, tactile receptors for light touch and texture - especially in the very sensitive, hairless areas - lips, eyelids, fingertips, palms, nipples, genitals 2. Free Nerve Endings - for warm, cold, and Nociceptors for pain 3. Merkle's Discs/Corpuscles/Cells Copyright © 2002 Michael H. Mitchell – All Rights Reserved - in base of  - Sudoriferous (Sweat) Glands 1. Merocrine or Eccrine - most in dermis - for evaporative cooling - sweat is released by exocytosis - Diaphoresis - excessive sweating as seen in various diseases 2. Apocrine (scent) - in axilla, groin, areolar, anal, bearded region of adult males - more fat and proteins than merocrine sweat so may be milky Copyright © 2002 Michael H. Mitchell – All Rights Reserved  - Sebaceous Glands - produce Sebum (oil) - at base of hairs - a type of Holocrine gland which release their contents when the cell ruptures - Pimples - inflamed sebaceous glands due to bacterial infection (usually Staphylococcus) - Hair (aka pili or pilus) Copyright © 2002 Michael H. Mitchell – All Rights Reserved  The Integumentary System - PATHOLOGY First degree Burns - This type of burn involves only the epidermis Second degree Burns - This type of burn reaches the dermis Third degree Burns - This type of burn reaches the hypodermis Decubitus Ulcer - bed sores caused by Ischemic Necrosis Copyright © 2002 Michael H. Mitchell – All Rights Reserved  Psoriasis - chronic - increased mitosis, increased keratin, silvery scales - may bleed if scraped off - especially on knees, elbows, scalp Eczema - acute - inflammation from allergies, infections, drugs, etc. - red, oozing, crusted, scaled lesions - as with poison ivy Impetigo - skin staphylococcus (bacterial) infection especially seen in Copyright © 2002 Michael H. Mitchell – All Rights Reserved  Urticaria = hives = wheals - due to Mast Cell "degranulation" i.e. the granules release their contents especially histamine Warts - caused by papillomaviruses - usually self limiting and regress spontaneously - Human Papilloma Virus (HPV) - STD causing venereal warts and over 99% Copyright © 2002 Michael H. Mitchell – All Rights Reserved  Neoplasms = Cancers 1. Basal Cell Carcinoma - from stratum basale to dermis - most frequent skin cancer - usually cured w/ surgery - little metastasis (spreading to other areas) - especially seen in areas exposed to sun 2. Squamous Cell Carcinoma - from Keratinocytes in stratum spinosum 2002 Michael Copyright-© also inH.areas Mitchell – All exposed Rights Reserved to sun