BIOH111 o Cell Module o Tissue Module o Skeletal system o Muscle system o Nervous system o Endocrine system o Integumentary system Endeavour College of Natural Health endeavour.edu.au 1
Textbook and required/recommended readings o Principles of anatomy and physiology. Tortora et al; 14 th edition: Chapter 5 Endeavour College of Natural Health endeavour.edu.au 2
BIOH111 INTEGUMENTARY SYSTEM MODULE o Session 24 (Lectures 47 and 48) Structure of the skin and accessory structures o Session 25 (Lectures 49 and 50) Function of the integumentary system and principles of wound healing Endeavour College of Natural Health endeavour.edu.au 3
BIOH111 Lectures 47 and 48 Structure of the skin and accessory structures Department of Bioscience endeavour.edu.au
Objectives Lecture 47: Structure of skin Define and describe the structure of each skin layer Lecture 48: Accessory skin structures Define and describe the structure of each accessory skin structure Endeavour College of Natural Health endeavour.edu.au 5
FUNCTIONS OF SKIN (also see session 25) o Thermoregulation o Blood reservoir o Protection o Cutaneous sensations o Synthesis of Vitamin D o Excretion Endeavour College of Natural Health endeavour.edu.au 6
GENERAL ANATOMY o Large organ composed of all 4 tissue types; 2m 2 in area; 1-2 mm thick; weight: 4.5 kg o 3 layers: 1. Epidermis: superficial portion; composed of epithelial tissue 2. Dermis: deeper layer; primarily composed of connective tissue 3. Hypodermis (or subcutaneous layer): deepest layer; consists of areolar and adipose tissue; not part of the skin www.webmd.com Endeavour College of Natural Health endeavour.edu.au 7
EPIDERMIS o Stratified squamous epithelium: avascular (contains no blood vessels) 4 types of cells divided into 5 distinct strata (layers) Endeavour College of Natural Health endeavour.edu.au 8
CELLS OF EPIDERMIS 1. Keratinocytes: produce keratin and contain lamellar granules function: help protect the skin and underlying tissue from heat, microbes, and chemicals; release lipids (waterproof) 2. Melanocytes: produce pigment melanin function: contribute to skin colour and absorb damaging ultraviolet (UV) light 3. Langerhans cells: derived from bone marrow function: participate in immune response 4. Merkel cells: contact tactile (Merkel) disc function: sensation of touch Endeavour College of Natural Health endeavour.edu.au 9
LAYERS (STRATA) OF THE EPIDERMIS Endeavour College of Natural Health endeavour.edu.au 10
STRATUM BASALE (STRATUM GERMINATIVUM) o Deepest single layer of epidermis o Cells: Merkel cells, melanocytes, keratinocytes and stem cells that divide repeatedly; cells attached to each other and to the basement membrane by desmosomes and hemidesmosomes Endeavour College of Natural Health endeavour.edu.au 11
STRATUM SPINOSUM o Cells: mostly keratinocytes; some melanocytes; 8 to 10 cell layers are held together by desmosomes o Function: provides strength and flexibility to the skin o Melanin is phagocytosed by keratinocytes after nearby melanocytes secrete it in secretory vesicles Endeavour College of Natural Health endeavour.edu.au 12
STRATUM GRANULOSUM o Transition layer between the deeper, metabolically active strata and the dead cells of the more superficial strata o Cells: keratinocytes which contain lamellar granules (release lipid that repels water) and dark-staining keratohyalin granules (keratohyalin converts tonofilaments into keratin); 3-5 layers of flat dying cells that show nuclear degeneration Endeavour College of Natural Health endeavour.edu.au 13
STRATUM LUCIDUM o Present only in the fingers tips, palms of the hands, and soles of the feet. o Three to five layers of clear, flat, dead keratinocytes that contain keratin precursor Endeavour College of Natural Health endeavour.edu.au 14
STRATUM CORNEUM o 25 to 30 layers of flat dead cells filled with keratin and surrounded by lipids from lamellar granules; continuously shed o Function: barrier to light, heat, water, chemicals and bacteria o Callus: an abnormal thickening of the epidermis with constant exposure to friction to this layer Endeavour College of Natural Health endeavour.edu.au 15
Epithelial differentiation KERATINIZATION www.studyblue.com o Keratinization is replacement of cell contents with the protein keratin; occurs as cells move to the skin surface over 2-4 weeks Endeavour College of Natural Health endeavour.edu.au 16
Non assessable Read Disorders: Homeostatic Imbalances (Tortora, p 287) and define following terms: rheumatism, osteoarthritis, rheumatoid arthritis, gouty arthritis, lyme disease, aging and strain/sprain. Then discuss: - How is psoriasis developed explain the normal skin biology and then apply it to psoriasis development - Think about the causes and possible treatments for psoriasis within your particular interest. Endeavour College of Natural Health endeavour.edu.au 17
Clinical application: o Skin Grafts: New skin can not regenerate if the stratum basale and its stem cells are destroyed Autograft: covering of wound with piece of healthy skin from self Isograft: from your identical twin Autologous skin: transplantation of patient s skin after it has grown in culture Endeavour College of Natural Health endeavour.edu.au 18
DERMIS o Structure: connective tissue layer composed of collagen and elastic fibers, fibroblasts, macrophages and adipocytes o Contains hair follicles, glands, nerves and blood vessels o Two major regions of dermis 1. Papillary region 2. Reticular region Endeavour College of Natural Health endeavour.edu.au 19
1. PAPILLARY REGION o Top 20% of dermis; finger-like projections are called dermal papillae o Structure: areolar connective tissue containing fine elastic fibers, Meissner s corpuscles, free nerve endings, adipose cells, hair follicles, sebaceous glands, sudoriferous glands o Functions: anchors dermis to epidermis; provides strength, extensibility (ability to stretch), and elasticity (ability to return to original shape after stretching) What is the function of the Meissner s corpuscules and free nerve endings? Endeavour College of Natural Health endeavour.edu.au 20
2. RETICULAR REGION o Bottom 80% of dermis o Structure: dense irregular connective tissue that contains interlacing collagen and elastic fibers; oil glands, sweat gland ducts, adipose and hair follicles o Function: provides strength, extensibility and elasticity to skin Endeavour College of Natural Health endeavour.edu.au 21
SKIN COLOUR PIGMENTS o Melanin: complex polymer derived from tyrosine; produced by melanocytes in epidermis UV in sunlight increases melanin production o Carotene: yellow-orange pigment (precursor of vitamin A); found in stratum corneum and dermis o Haemoglobin: red, oxygen-carrying pigment in blood cells if other pigments are not present, epidermis is translucent so pinkness will be evident Endeavour College of Natural Health endeavour.edu.au 22
Clinical application The colour of skin and mucous membranes can provide clues for diagnosing certain problems, such as Jaundice Yellowish colour to skin and the whites of eyes Buildup of yellow bilirubin in blood from liver disease Cyanosis Bluish colour to nail beds and skin Haemoglobin depleted of oxygen looks purple-blue Erythema Redness of skin due to enlargement of capillaries in the dermis During inflammation, infection, allergy or burns Endeavour College of Natural Health endeavour.edu.au 23
Clinical application Common disorders linked to melanocytes and melanin biology are freckles (liver spots), albinism and vitiligo. In groups of 3-4, pick one disorder and consider: - Cause of the disorder - Explain skin biology and how is it impacted by the disorder - Consider any appropriate treatment within your own interests Endeavour College of Natural Health endeavour.edu.au 24
TYPES OF SKIN o Thin skin Covers all parts of the body except for the palms and palmar surfaces of the digits and toes Lacks epidermal ridges Has a sparser distribution of sensory receptors than thick skin o Thick skin (0.6 to 4.5 mm) Covers the palms, palmar surfaces of the digits, and soles Features stratum lucidum and thick epidermal ridges Lacks hair follicles, arrector pili muscles, and sebaceous glands, and has more sweat glands than thin skin Endeavour College of Natural Health endeavour.edu.au 25
Objectives Lecture 47: Structure of skin Define and describe the structure of each skin layer Lecture 48: Accessory skin structures Define and describe the structure of each accessory skin structure Endeavour College of Natural Health endeavour.edu.au 26
ACCESSORY STRUCTURES OF SKIN o Develop from the embryonic epidermis o Cells sink inward during development to form: Hair Oil glands Sweat glands Nails Endeavour College of Natural Health endeavour.edu.au 27
HAIR (PILI) o Present everywhere except palms, palmar surfaces of the digits, soles and plantar surfaces of the digits. o Structure: Shaft: above the skin surface Root: penetrates the dermis and subcutaneous layer Cuticle Follicle o New hairs develop from cell division of the matrix in the bulb o Function: prevents heat loss; decreases sunburn; eye protection (eyelashes); senses light touch (hair root plexus) Endeavour College of Natural Health endeavour.edu.au 28
HAIR GROWTH o The hair growth cycle consists of 2 stages: 1. Growth stage lasts for 2 to 6 years; matrix cells at base of hair root producing length 2. Resting stage o lasts for 3 months; matrix cells inactive and follicle atrophies Old hair falls out as growth stage begins again (normal hair loss is 70 to 100 hairs per day) o Rate of growth and replacement cycle can be altered by illness, diet, high fever, surgery, blood loss, severe emotional stress, and gender; hormones influence the growth and loss of hair; chemotherapeutic agents affect the rapidly dividing matrix hair cells resulting in hair loss. Endeavour College of Natural Health endeavour.edu.au 29
TYPES OF HAIR 1. Lanugo fine, non-pigmented hair; covers the foetus 2. Vellus hair short, fine hair that replaces lanugo; invisible to naked eye 3. Terminal hair course pigmented hair; appears in response to androgens and hair of the head; first eyelashes and eyebrows, then other body regions Endeavour College of Natural Health endeavour.edu.au 30
HAIR COLOUR o Hair colour is due primarily to the amount and type of melanin o Graying of hair occurs because of a progressive decline in tyrosinase decline in melanin production Dark hair contains true melanin Blond and red hair contain melanin with iron and sulphur added White hair has air bubbles in the medullary shaft Endeavour College of Natural Health endeavour.edu.au 31
GLANDS OF THE SKIN o Specialized exocrine glands found in dermis 1. Sebaceous (oil) glands 2. Sudoriferous (sweat) glands 3. Ceruminous (wax) glands 4. Mammary (milk) glands Endeavour College of Natural Health endeavour.edu.au 32
SEBACEOUS (OIL) GLANDS o Sebaceous (oil) glands are usually connected to hair follicles; they are absent in the palms and soles; secretory portion of gland is located in the dermis o Produce sebum Contains cholesterol, proteins, fats and salts Moistens hairs Waterproofs and softens the skin Inhibits growth of bacteria and fungi (ringworm) o Clinical application: Acne Bacterial inflammation of glands Secretions are stimulated by hormones at puberty gazettereview.com Endeavour College of Natural Health endeavour.edu.au 33
SUDORIFEROUS (SWEAT) GLANDS 1. Eccrine sweat glands: extensive distribution to most areas of skin; secretory portion is in dermis with duct to surface terminate at pores at the surface of the epidermis Regulate body temperature through evaporation (perspiration) Help eliminate wastes such as urea Secretions are more viscous 2. Apocrine sweat glands: limited in distribution to the skin of the axilla, pubis, and areolae; secretory portion in dermis; ducts open into hair follicles health.howstuffworks.com Endeavour College of Natural Health endeavour.edu.au 34
CERUMINOUS GLANDS o Modified sudoriferous glands that produce a waxy substance called cerumen Found in the outer ear Barrier for entrance of foreign bodies o Abnormal amount of cerumen in the outer ear canal can result in blockage and prevent sound waves from reaching the ear drum. Endeavour College of Natural Health endeavour.edu.au 35
STRUCTURE OF NAILS o Tightly packed keratinized cells o Nail body: Visible portion pink due to underlying capillaries Free edge appears white o Nail root: Buried under skin layers Lunula is white due to thickened stratum basale o Eponychium (cuticle): Stratum corneum layer Endeavour College of Natural Health endeavour.edu.au 36
NAIL GROWTH o Nail matrix is below nail root - produces growth o Cells transformed into tightly packed keratinized cells 1 mm per week o Certain nail conditions may indicate disease Endeavour College of Natural Health endeavour.edu.au 37
COMMONWEALTH OF AUSTRALIA Copyright Regulations 1969 WARNING This material has been reproduced and communicated to you by or on behalf of the Endeavour College of Natural Health pursuant to Part VB of the Copyright Act 1968 (the Act). The material in this communication may be subject to copyright under the Act. Any further reproduction or communication of this material by you may be the subject of copyright protection under the Act. Do not remove this notice. Endeavour College of Natural Health endeavour.edu.au 38