Chapter 4, Tissues & Skin PDF

CHAPTER 4 Introduction to tissues and the skin. Objectives 4 types of tissues, especially epithelial and connective tissues Skin as an organ system  Tissues Four primary tissues: Epithelial tissue: lines the body’s surfaces (epidermis, inner lining of blood vessels and heart...

CHAPTER 4 Introduction to tissues and the skin. Objectives 4 types of tissues, especially epithelial and connective tissues Skin as an organ system  Tissues Four primary tissues: Epithelial tissue: lines the body’s surfaces (epidermis, inner lining of blood vessels and heart, inner lining of digestive tract including inside cheek, inner lung surfaces) Connective tissue: connects and holds various parts of the body together (tendons, ligaments, cartilage, bone, adipose tissue, dermis, hypodermis, outer lining of organs like digestive system and blood vessels) Muscle tissue: contracts for motion (skeletal, cardiac, smooth) Nervous tissue: generate electrical signals for transmitting information  Epithelial Tissues Line body cavities and cover surfaces Consist of sheets of connected cells Simple (one layer): permits exchange, secretion of substances Stratified (multiple layers): protection from abrasion and infection  Glands: epithelial tissue Glandular epithelia: create and secrete certain chemicals Exocrine glands: secretion into hollow organs: saliva into the mouth, digestive acids and enzymes into stomach Endocrine glands: hormones secreted into the blood Copyright © 2001 Benjamin Cummings, an imprint of Addison Wesley Longman, Inc. Slide 4.2  Connective Tissue Supports and Connects Body Parts Connective tissue: cells are not densely packed together, the protein matrix (a cell product) is the most important part of the connective tissue. Connective tissue is “fibrous” or “specialized” Fibrous Connective Tissue The protein matrix Collagen fibers (strength, some flexibility) Elastin fibers (stretchy, flexible) Reticular fibers (thinner collagen, provides support) Cells of fibrous connective tissue Fibroblasts (produce protein matrix), white blood cells, fat storage cells The ground substance Gel-like: polysaccharides, water, proteins Loose, Fibrous Connective Tissue Connective Tissue Supports and Connects Body Parts Fibrous connective tissue types Loose: Surrounds many internal organs, muscles and blood vessels. Flexible, not very strong, collagen/elastin fibers randomly oriented. This is the most common. Dense, irregular: (dermis). Similar to loose connective tissue, but denser collagen fibers so stronger, less flexible. Surrounds organs that do not stretch much (kidneys) Elastic: Surrounds stomach, bladder, and other organs that need to change shape often, with more elastin fibers. Dense, regular: tendons (connect muscle - bone), ligaments (connect bone-bone), parallel-arranged collagen fibers Loose versus dense, regular connective tissue Specialized connective tissue Cartilage Bone Blood Adipose tissue  Specialized connective tissue: cartilage Cartilage: chondroblasts construct the protein matrix, and are then imprisoned within. No blood vessels in cartilage = heals very slowly. Collagen and elastin in rubbery ground substance, flexible yet solid. Hyaline cartilage: small collagen fibers, very smooth. Found: at end of bones at synovial joints to reduce friction, part of nose, joins ribs to sternum, keeps trachea open, forms early fetal skeleton (later converted to bone). Elastic cartilage: collagen fibers with more elastin = more flexible. Found: ears, epiglottis that covers trachea. Fibrocartilage: thick collagen bundles, can withstand pressure. Found: vertebral disks, cushions in knees Slide 4.6B Specialized connective tissue: bone Bone: collagen fibers, elastin fibers and hardened inorganic matrix from calcium and phosphate. Osteocyte cells are few, are in contact with each other and blood vessels for nutrient/waste exchange (can heal quickly). Specialized connective tissue: blood Blood: plasma, red blood cells, white blood cells and platelets. Blood cells originate in red bone marrow of humerus, femur, sternum and other bones. Intercellular transport, immune system and clot formation. Specialized connective tissue: adipose tissue Adipose tissue with fat cells: function in insulation (hypodermis), cushion kidneys, and energy (fat) storage Organs and Organ Systems Perform Complex Functions Tissues form individual organs, and groups of coordinated organs form organ systems Integument system Nervous system Skeletal system Sensory systems Muscular system Endocrine system Blood Digestive system Circulatory system Urinary system Immune system Reproductive systems Respiratory system Skin: Integument System Skin: Functions Prevents dehydration (keratin protein) Protects muscles / bones from injury (scrapes and cuts) Defends against infection (pH 5 - 6, epidermis forms barrier, contains white blood cells that destroy bacteria) Regulates body temperature (sweat, blood flow, insulation) Sensation (light touch, deep pressure, temperature, vibrations, movement of hairs, pain) Important for making vitamin D (with UV light) Protects underlying cells from UV light (melanin pigment) Advantages and disadvantages of different skin colors Dark skin: Protection from skin cancer in sunny regions (low latitudes), problems with vitamin D production in less sunny regions (high latitudes). Light skin: Problems with skin cancer in sunny regions, more production of vitamin D in less sunny regions.  Outermost layer: dead, The epidermis flattened keratinocyte cells. Keratin proteins provide a (epithelial tissue) nearly waterproof outer layer. Living epidermal cells move towards the surface, later they die (they become too far away from blood vessels) Melanocytes produce melanin pigment, which protects you from ultraviolet light, that can cause mutations which cause skin cancer.  Dermis: collagen fibers mostly (dense, irregular connective tissue) Hair: formed by dead, flattened keratinocyte cells: forms at base and pushed upwards. Smooth muscle and nerve attachments. When does our hair stand up? Oil glands: oil secretions moisten and softens skin and hair Sweat glands: for cooling us down Blood vessels: supply nutrients and oxygen, remove waste, for temperature regulation Sensory nerve endings: for heat, cold, light touch, deep pressure, vibrations, pain (excessive pressure, excessive temperatures and slow pain) White blood cells: for defense Hypodermis: Adipose tissue, with fat cells for insulation