W2.Skin & Subcutaneous Tissues. Dr. A Alraddadi.2023-2024.pdf

Skin & Subcutaneous Tissues (Week 2) Dr. Abdulrahman Alraddadi Assistant Professor of Human Anatomy BMS-COM- KSAUHS Office N: 1.CM.2.311 Emails: [email protected], [email protected] Office: 0114295280  Learning Objectives By the end of the session the student should be...

Skin & Subcutaneous Tissues (Week 2) Dr. Abdulrahman Alraddadi Assistant Professor of Human Anatomy BMS-COM- KSAUHS Office N: 1.CM.2.311 Emails: [email protected], [email protected] Office: 0114295280  Learning Objectives By the end of the session the student should be able to: Name the two major layers of the skin and the tissue of which each is made. List the cells of the skin and describe their function and location. Identify the skin appendages (hair, nails, sebaceous and sweat glands) and describe their functions. Name the cutaneous senses and explain their importance. Describe how the arterioles in the dermis respond to heat, cold, and stress. Name the tissues that make up the subcutaneous tissue, and describe their functions. 25/08/2024 DR. A ALRADDADI 2 Lecture Outline Introduction Layers of Skin Cutaneous Derivatives Cutaneous Glands Skin Receptors Clinical Considerations Discussion 25/08/2024 DR. A ALRADDADI 3  Function of Skin Protection: protects the body against pathogens and damage from external environment Sensation: contains nerve endings and receptors for touch, pressure, vibration, pain and temperature Thermoregulation: regulates body temperature by control blood flow to skin and sweat production Evaporation Control: semi-impermeable barrier to fluid loss Storage and Synthesis: store lipids and synthesis of vitamin D Absorption: small amounts of oxygen, nitrogen, carbon dioxide can diffuse into the epidermis 25/08/2024 DR. A ALRADDADI 4 Layers of Skin 25/08/2024 DR. A ALRADDADI 5  Layers of Skin 1. Epidermis: A superficial thin layer of modified stratified squamous epithelium 2. Dermis: Thick layer of fibroblastic connective tissue Hypodermis: Subcutaneous connective tissue of a loose fibroblastic tissue Adipose tissue Lies deep to the dermis, & is equivalent to the superficial fascia of gross Anatomy 25/08/2024 DR. A ALRADDADI 6  Layers of Skin Each layer of skin consists of sub-layers Epidermis consists of five layers of cells which represent phases of maturation (from superficial to deep): 1. Stratum Corneum (most external) 2. Stratum Lucidum 3. Stratum Granulosum 4. Stratum Spinosum 5. Stratum Basale (stratum germinativum) Dermis consists of 2 layers of connective tissue: a. Papillary layer b. Reticular layer 25/08/2024 DR. A ALRADDADI 7 25/08/2024 DR. A ALRADDADI 8  Phases of Maturation of Epidermis 25/08/2024 DR. A ALRADDADI 9  Epidermis Cells Keratinocytes: Make up the majority of the cells (about 90%) in the epidermis Produce keratin and involved in keratinization Melanocytes: Pigment (melanin) producing cells Melanin granules are injected into keratinocytes (mainly in the St. Germinativum) Langerhans Cells: Found in all layers; mainly in the St. Spinosum Involved in preparing cutaneous antigens Merkel Cells: Usually located in thick skin (in stratum basale) Free nerve endings often form a disk adjacent to these cells Sensitive to touch (mechanoreceptors) 25/08/2024 DR. A ALRADDADI 10  Epidermis Cells Merkel Cells Melanocytes Keratinocytes Langerhans Cells #Clear, ovoid and may # Appear as round cells with # Desmosomes are a type of #They have an oval, reniform occur singly or in clusters pale staining cytoplasm junction that join cells of the or irregular pale nucleus in the stratum basale scattered among the cells of epidermis together. They surrounded by pale-staining basal layer are frequent in he stratum cytoplasm. spinosum. 25/08/2024 DR. A ALRADDADI 11  Layers of Skin: Dermis Papillary Layer: Narrow zone of loose connective tissue below the epidermis Cellular component of the dermis: mainly fibroblasts responsible for production of collagen & elastin. Contains numerous capillaries and nerve endings Reticular Layer: Considerably thicker and less cellular than papillary dermis. Broad, dense layer of connective tissue Contains many interlacing bundles of collagenous fibers 25/08/2024 DR. A ALRADDADI 12  Types of Skin 1. Thick Skin: Form the palms of the hands and the soles of the feet 2. Thin Skin: Form any part of the body except palmar and plantar surfaces 25/08/2024 DR. A ALRADDADI 13 Differences Between Thick & Thin Skins 5layers 4 layers Prominent Less prominent stratum stratum corneum corneum No stratum Well developed Lucidum stratum granulosum Less developed stratum Palms of the granulosum hands & soles Dominant & of the feet lines most of Thinner dermis the body No hair & surface sebaceous Thicker dermis glands Hair & sebaceous glands 25/08/2024 DR. A ALRADDADI 14 Differences Between Thick & Thin Skins 25/08/2024 DR. A ALRADDADI 15  Subcutaneous Tissue Superficial fascia Connective tissue membrane A. Loose connective tissue Collagen & elastin fibers, WBC, & mast cells Connects skin to muscles B. Adipose tissue Fat tissue Cushions bony prominences Provides some insulation from cold Subcutaneous Tissue  Circulation of the Skin Function: Nutrition of the skin and appendages Increased blood flow to facilitate thermoregulation The Arteries Supplying: Superficial blood vessels deep in the subcutis Two plexuses: a. Cutaneous plexus → at the junction of the subcutis and dermis b. Subpapillary plexus → at the junction between papillary and reticular dermis ❑ Gives rise to a capillary loop in each dermal papilla The Venous & Lymphatic Drainage: Arranged into plexuses broadly corresponding to the arterial supply 25/08/2024 DR. A ALRADDADI 18  Circulation of the Skin Arterioles: Plays an important role in thermoregulation: by controlling blood flow to the dermis In warm environment → Vasodilation: increase the blood flow to skin → brings heat to the body surface In cold environment → Vasoconstriction: decrease the blood flow to skin → keeps the heat within the body core In stress situation → Vasoconstriction: shunt blood to more vital organs Prolonged pressure on the skin → decrease the blood supply to the skin → decubitus ulcers (pressure/ bed sores) 25/08/2024 DR. A ALRADDADI 19  The Tension Lines Also called Cleavage Lines or Langer’s Lines Spiral longitudinally in the limbs and transversely in the neck and trunk The pattern of collagen fibers determines the characteristic tension and wrinkle lines in the skin With age, the elastic fibers of the dermis deteriorate and are not replaced; consequently, in older people, the skin wrinkles and sags as it loses its elasticity Lacerations or incisions that parallel the tension lines → heal well with little scarring Laceration or incision across the tension lines → disrupts more collagen fibers and skin lines causing the wound to gape and it may heal with excessive (keloid) scarring 25/08/2024 DR. A ALRADDADI 20  Rule of 9’s Total Surface area of skin of the body is divided percentage-wise and is used clinically to assess the need for fluid replacement therapy after burns 25/08/2024 DR. A ALRADDADI 21  Burns 1st Degree Burn (superficial): The superficial epidermis 2nd Degree Burn (partial-thickness): The epidermis + dermis (affected) 3rd Degree Burn (full-thickness burn): The epidermis + dermis +/- subcutaneous tissue 4th Degree Burn (deep full-thickness) The epidermis + dermis + subcutaneous tissue + muscle tissue + bone Cutaneous Derivatives 25/08/2024 DR. A ALRADDADI 23 Cutaneous Derivatives, Glands, Smooth Muscle Derivatives: Hair Nails Glands: Small (Merocrine) Sweat Glands Large (Apocrine) Sweat Glands Sebaceous Glands Smooth Muscle in the Skin: Arrector Pili Muscle Myoepithelial Cells 25/08/2024 DR. A ALRADDADI 24  Cutaneous Derivatives: Hair Function: Protection against dust & germs, & thermal insulation Hair Follicle: It formed of epithelial cells Derived from a cylindrical invagination of epidermis called a hair follicle The pilosebaceous unit: Consists of: a. Follicle b. Attached smooth muscle (arrector pili/ pilomotor muscle) c. A sebaceous gland 25/08/2024 DR. A ALRADDADI 25  Cutaneous Derivatives: Hair The structure of the hair follicle consist of the following: 1. Dermal papilla: At the base of the follicle A projection of connective tissue of the dermis Contain blood vessels 2. Hair root: Above the dermal papilla Contain the matrix cells (place of mitosis) New cells produce keratin + get their color from melanin 3. Hair shaft: Consist of dead, keratinized cells Monthly hair growth rate = 0.3 – 0.4 in (8 – 10 mm) Daily hair loss = 50 – 100 hairs per day 25/08/2024 DR. A ALRADDADI 26 Smooth Muscle in the Skin: Arrector Pili Muscles Oblique bands of smooth muscle Attached at the deeper ends to the connective tissue sheath of the hair follicles (Insertion) and at their opposite ends to the superficial parts of the dermis (Origin). Stimulated by cold or emotions → pull the hair follicles upright (piloerection/ goose bumps). 25/08/2024 DR. A ALRADDADI 27  Cutaneous Derivatives: Nails It consists of keratinized dead cells Presented at the ends of fingers and toes Function: protection, pick up small objects, scratching The production of the nail cells occur in the nail root at the base of the nail The new cells produce keratin (stronger than that of the hair) and then die The structure of the nail consist of: − Nail Bed: living epidermis & dermis − Root, Body, and Free Edge of the Nail − Nail Fold: skin surrounding the sides of the nail − Cuticle: layer of cells which grows out from the proximal nail fold onto the surface of the nail 25/08/2024 DR. A ALRADDADI 28 Cutaneous Glands 25/08/2024 DR. A ALRADDADI 29 Cutaneous Glands: Small (Merocrine) Sweat Glands Simple convoluted tubular glands Secret a watery fluid onto the surface of the skin. 25/08/2024 DR. A ALRADDADI 30 Cutaneous Glands: Large (Apocrine) Sweat Glands Simple convoluted tubular glans Slightly branched Found in the axilla, in the areola, in the perianal region, and in the eyelids Activated by stress and emotions 25/08/2024 DR. A ALRADDADI 31 Cutaneous Glands: Sebaceous Glands Small, compound alveolar glands Holocrine glands The duct opens into hair follicle or onto the epidermis Secrete sebum (lipid) into hair follicles or to the skin surface The fatty acids of sebum inhibit the growth of some bacteria and prevent drying of skin and hair. Overactive sebaceous glands + inflammation = acne 25/08/2024 DR. A ALRADDADI 32  Cutaneous Glands: Cerumen Glands Secrete cerumen (earwax) in the ear canals Cerumen prevents drying of the eardrum Excess cerumen → impacted against the eardrum → might diminish the acuity of hearing (by preventing the eardrum from vibrating properly) https://www.pinterest.com/pin/397090892129858188/ 25/08/2024 DR. A ALRADDADI 33 Skin Receptors 25/08/2024 DR. A ALRADDADI 34  Skin Receptors Receptors detect changes on or in the skin (touch, pressure, heat, cold, itch, and pain) Provide information about the external environment that initiates appropriate responses Sensitivity of the skin depends on the number of receptors present Mostly located in the dermis A. Free nerve endings: for heat, cold, itch, and pain B. Encapsulated Nerve Endings: For touch and pressure Pacinian corpuscles https://www.pinterest.com/price3690/ Meissner's corpuscles  Pacinian corpuscles Onion skin arrangement Sensitive to: Deep pressure Stretch Vibration of high frequency Rapidly adapting Found in subcutaneous tissue 25/08/2024 DR. A ALRADDADI 36  Meissner's corpuscles Found in the dermal papilla Has oval, capsule surrounding mass of plump oval cells arranged transversely Located in finger tips, sole, nipple, eye lid, genitalia and lips Sensitive light discriminatory touch 25/08/2024 DR. A ALRADDADI 37 Clinical Consideration  Clinical Consideration Skin Cancer Cause: exposure to sunlight A. Squamous cell carcinoma and basal cell carcinoma Most common type Changes in the normal appearance Do not metastasize B. Malignant melanoma More serious Begins in melanocytes It may metastasize  Clinical Consideration Autoimmune Disease A. Alopecia Areata Hair is lost in discrete patches Common in the scalp The immune system targets the growing portions of hair follicles B. Plaques of Psoriasis Faulty lymphocyte activity Causes an overgrowth of the cells of the lower epidermis Results in red patches of skin with visible scaling of the stratum corneum  Clinical Consideration Common Skin Disorders A. Impetigo Bacterial infection by streptococci or staphylococci Pus-containing lesions It is contagious B. Eczema Changes the chemistry and structure of the skin Weak tight junctions between epidermal cells Causing water to evaporate through the skin, and bacteria or other irritants to enter the skin.  Clinical Consideration Common Skin Disorders C. Warts: Caused by a virus Epidermal cells divide abnormally, producing a raised growth tissue with a rough or pitted surface Most common on the hands D. Fever Blisters (Cold sores) Caused by the herpes simplex virus Common at the edge of the lip  References Valerie C.Scanlon and Tina Sanders ,Essentials of anatomy and physiology ,8th edition.,2018, ISBN10 0803669372, ISBN13 9780803669376,FA Davis Company Gray's Anatomy for Students. 4th Edition. Richard L. Drake, Wayne Vogl, and Adam W.M. Mitchell. Elsevier Churchill Livingstone. Junquiera’s Basic histology : Text and Atlas,Anthony Mescher,15th edition 8/25/2024 Dr. A Alraddadi 43 Assignment 1. Which of the following diseases characterized with hairless patches? A. Alopecia areata B. Eczema C. Impetigo D. Psoriasis 2. Which of the following concerning the dermis is true? A. Consist of basal and reticular layers B. Formed by adipose tissue C. Found between the epidermis and subcutaneous tissue D. Has cellular component of chondrocytes 3. Where the free nerve endings for the pain is located? A. Papillary layer of dermis B. Reticular layer of dermis C. Stratum spinosum D. Subcutaneous tissue 4. Which of the following concerning the eczema is true? A. Changes in the chemistry of the skin only B. Changes in the structure of the skin only C. Weak tight junction between the epidermal cells D. Weak tight junctions between the dermal cells 5. Which of the following form the layers of the skin? A. Dermis B. Dermis and epidermis C. Dermis, epidermis, and subcutaneous tissue D. Dermis, epidermis, and superficial tissue 6. Which of the following is sensitive to touch? A. Astrocyte B. Chondroblast C. Fibroblast D. Merkel cell 7. A patient brought to the ER with a burn wound penetrates the subcutaneous tissue. Which of the following is most likely the classification of burn? A. 1st degree B. 2nd degree C. 3rd degree D. 4th degree 8. Which of the following glands produce earwax? A. Cerumen gland B. Large sweat gland C. Sebaceous gland D. Small sweat gland 9. Where the production of the new nail cell take place? A. Nail bed B. Bail body C. Nail free edge D. Nail root 10. Which of the following is true concerning the thermoregulation of the skin in warm environment? A. Decrease the blood flow to skin B. Goose bumps reaction C. Increase the blood flow to skin D. Sweating reaction