03 - Tissues & Intrgument (handout) 2024.pdf

Tissues & The Integument Human Anatomy & Physiology 2024-2025 HTHSCI 1H06 A/B McMaster Mohawk Lecture Outline Today we will: Introduce the four types of tissues Focusing on epithelial and connective tissues Discuss the Integumentary system Structure and function...

Tissues & The Integument Human Anatomy & Physiology 2024-2025 HTHSCI 1H06 A/B McMaster Mohawk Lecture Outline Today we will: Introduce the four types of tissues Focusing on epithelial and connective tissues Discuss the Integumentary system Structure and function Epidermis and dermis Skin glands Six functions of the skin Four Types of Tissue 1. Epithelial (covering) 2. Muscle (movement) 3. Nervous (control) 4. Connective (support) Epithelial Tissue Classification Epithelial tissue is classified according to the number of cells layers and their shape Note: epithelial tissue is avascular (a = without, vascular = vessel) Epithelial Tissue Examples Apical Lateral Basal Simple columnar Basement Simple cuboidal Stratified membrane squamous Pseudostratified, ciliated columnar Connective Tissue Binding and support Connective tissues is the most abundant tissue by weight, usually well vascularized, and serves several functions including: ❑ binding and support ❑ protection against infection ❑ tissue repair ❑ insulation Consists of cells surrounded by an extra-cellular matrix (ECM) ECM = ground substance + protein fibers (3 types: collagen, elastin, reticular) Ground substance may be fluid, semi fluid, gelatinous or calcified Different amounts of fiber types and cell types produce the different classes of connective tissue.  Classes of Connective Tissue (1) Connective tissue proper (2) Cartilage Fibroblasts Loose connective tissue Adipocytes* hyaline (semi-fluid GS) areolar fibrous reticular elastic adipose* Dense connective tissue Chondrocytes (stiff, gelatinous GS) regular Fibroblasts (very little GS) irregular elastic (3) Bone (4) Blood & Lymph RBCs / WBCs Osteocytes (fluid GS) (calcified GS) The Integument Human Anatomy & Physiology 2024-2025 HTHSCI 1H06 A/B McMaster Mohawk Clinical Connection The skin is an indicator of clinical conditions and dysfunction: Blue (Cyanotic) – Hypoxemia Yellow (Jaundiced / Icteric) – Liver dysfunction (bilirubin) Red (Erythema) – Heat, Infection, Inflammation, Allergic reaction White (Pallor) – Shock, Anemia, Peripheral vasoconstriction The Integumentary System Skin + accessory organs = integumentary system ‘tegere’ is Latin for ‘covering’ Consists of two layers: 1) Epidermis 2) Dermis Hair follicles Glands Sensory receptors Blood vessels Sits on the hypodermis (aka subcutaneous layer) Greek - hypo = under; dermo = skin Epidermis Cell types Melanocyte: Keratinocytes: 8% of epidermal cells Predominant cell type Produce melanin (90%) (protection from UV; Produce keratin hair colour & skin tone) (protect from heat, Stratum basale abrasion, microbes, chemicals, water) Langerhans cell: Merkel cell: Intraepidermal Detect touch sensations macrophage Stratum basale Phagocytosis Stratum spinosum Epidermis Strata Composed of 5 layers (strata): Corneum (horny) 25-30 layers of dead cells Lucidum (clear) Only present in thick skin* Granulosum (granular) 3-5 layers of cells Transition zone (living-dead) Keratohyalin Lamellar granules Spinosum (spiny) 8-10 layers Keratin intermediate filaments Cells joined by Desmosomes Basale (germinativum) Lacks blood vessels – nutrients via diffusion From which all other layers are Balance between cell production and cell loss (apoptosis; sloughing) derived (dividing layer) Entire process takes 4-6 weeks (7-10 days in psoriasis) Epidermis Epidermal ridges A series of elevations in a pattern of straight lines, loops or whorls Epidermal ridge on the palmar surface of the hands and digits and the plantar surface of the feet and toes. Gives rise to fingerprints and footprints. Serve to increase surface area of Epidermal peg the epidermis (e.g., improves grip). Consists of epidermal pegs supported by dermal papilla. Increases contact between dermis and epidermis to withstand mechanical stress. Structural Basis of Skin Tone Expression of 3 pigments: 1) Melanin (mainly) yellow-red / brown-black 2) Carotene (vitamin A) yellow-orange 3) Hemoglobin red Exposure to UV radiation increases the risk of skin cancer especially in individuals with lighter skin tones...  BENIGN MALIGNANT Melanomas symmetrical Asymmetrical Malignant melanomas arise from melanocytes Often nevi (moles) borders even Borders uneven Represent 2% of all skin cancers – metastasize quickly and can kill within months of Dx Risk factors for skin cancer include: one color Colours – two Skin type or more Sun exposure Family Hx Age diameter Diameter Immunologic status less than 6mm larger than 6mm Elevated or Evolving Dermis Structure Deeper and thicker than the epidermis Binds the epidermis to the underlying Epidermis tissues papillary Contains collagen and elastic fibers that provide support for the skin Dermis (secreted by Fibroblasts) reticular Location of BVs, nerves, hair follicles, and skin glands Divided into papillary and reticular regions Dermis Skin glands Types of skin glands: 1. Sebaceous (oils) 2. Apocrine (milky) Sweat 3. Eccrine (clear) (sudoriferous) 4. Ceruminous (waxy) Arrector Sebaceous pili m. Regulated by the SNS Eccrine Apocrine Functions of the Skin 1. Thermoregulation 2. Blood reservoir 3. Protection from the environment 4. Cutaneous sensations 5. Excretion and absorption (minor) 6. Synthesis of vitamin D Functions of the Skin (con’t) Thermoregulation The skin contributes to Lose heat when warm by directing blood to the epidermis maintaining a body temperature of 37oC Blood vessels dilate (to lose heat) or constrict (to conserve heat) Heat loss is promoted by sweat production (conduction & convection) Conserve heat when cold by directing blood away from epidermis Functions of the Skin (con’t) Blood Reservoir & Protection Blood Reservoir Dermis carries 8-10% of total blood volume Protection from the Environment Chemical Oily secretions (sebum) containing defensins, and low pH sweat, help retard the growth of microbes Melanin protects stem cells from damaging UV rays Physical Continuity (no breaks) Designed to withstand abrasion (thickness and keratin) Biological Intraepidermal macrophages provide immune surveillance and help activate other immune cells Functions of the Skin (con’t) Cutaneous Sensations, Excretion & Absorption, Metabolism Cutaneous Sensations Conveys external sensations to the spinal cord: Pain, temperature, touch, pressure, etc. Excretion & Absorption Waste products such as ammonia and urea excreted with sweat. A source of “insensible” H2O loss. Absorbs lipids, gases, and organic solvents Metabolism Contributes to synthesis of Vitamin-D → Ca2+ homeostasis Synthesis of Vit-D precursor requires UV exposure – further metabolized by liver and kidney Summary Today we: Introduced the 4 types of tissues Focusing on epithelial and connective tissues Discussed the structure & function of the integumentary system Next time An overview of the nervous system & how electrical signals are generated