ch4 Tissues & membranes + Ch5 Integumentary System

· Tissue- Group of similar cells collected together by an intercellular matrix · Intercellular Matrix- non-living material that fills the space between the cells o May contain salts and fibers unique to that kind of tissue · Histology- Study of tissues 4 types of tissue found in the body Epithelial-Connective-Muscle-Nervous 1. Epithelial- Covers the body surface, lines body cavities and covers organs · Structure- o Tightly packed cells with little intercellular matrix o 1 free surface where no cellular elements adhere § Microvillae and cilia o Avascular (no blood vessels) · Characteristics- Characterized by the shape of cells and number of layers o Reproduces readily (mitotic) o Squamous, cuboidal or columnar in shape o May be arranged in single (simple) or multiple (stratified) layers · Functions- o Protection, absorption and secretion -Simple Squamous: Single layer of flat cells · Found in alveoli (lungs) and capillaries and renal corpuscles of kidneys · Well suited for diffusion and filtration -Simple cuboidal: Single layer of cube shaped cells · Found in kidney tubules where it functions in absorption and in glandular tissue (thyroid and salivary glands) where it functions in secretion -Simple columnar: Single layer of column shaped cells · Found in the lining of the stomach and intestines where it functions in secretion and absorption · Has microvillae and goblet cells o Microvillae- small projections of the membrane § Aids in the absorption of nutrients and increases the surface area o Goblet cells- secrete mucus o Cilia- moves secretions along the surface § Hairlike processes that project from the membrane -Pseudostratified columnar: appears to have multiple layers but doesn’t · Cilia and goblet cells are associated with this · Lines portions of the respiratory and some tubes of the reproductive tracts -Stratified squamous: functions primarily to protect · Forms the outer layer of the skin, mouth, anus and vagina -Transitional: stratified (several layers) · Stretches in response to tension · Found in the bladder -glandular: specialized cells that produce and secrete substances · Found deep to the epithelium o Exocrine gland- secretes its product onto a free surface via a duct § Breast milk, sweat, mucus and saliva o Endocrine gland- secretes its product into blood § Ductless gland that secretes hormones · Hormones- chemical messengers that travel throughout the body to mediate functions in the body o Thyroid gland If it has only 1 cell it’s unicellular (goblet cell) If it has more than 1 cell it’s multicellular. Most are multicellular and have a secretory portion and a duct (salvatory and mamory glands) · Characteristics: o Simple gland – duct without branches o Compound gland – duct with branches o Tubular- gland and duct merge with no change in diameter o Acinar/alveolar- glands whose distal part forms a sack-like structure Classification of glands Based on mode of secretion · Merocrine glands- secretes a fluid that’s released through a cell membrane by exocytosis o Cell remains in-tact- no loss of cytoplasm o Most glandular cells are merocrine § Salavory and certain sweat glands o Cells of merocrine are either cerous are mucus § Cerous secrete thin watery cerous fluid that usually contains enzymes (saliva) § Mucous cells secrete thick fluid (mucous) (respiratory tract and intestines · Apocrine glands- Secratory product accumulates in 1 region of the cell and that portion pinches off and is lost with the secretion. The cell repairs and the process repeats · Holocrine glands- Cells become filled with secretory product, ruptures and the product is released 2. Connective Tissue- Binds structures together · Function- o Binds structures together o Forms the framework and support for organs and the body as a whole o Stores fat and transports substances o Protects against disease and helps repair tissue damage · Characteristics- o Has good blood supply and reproduces, but not as quickly as epithelial tissues o Has an abundance of intercellular matrix with relatively few cells § 2 types of fibers imbedded in the matrix are strong and flexible · Collagenous (white) fibers- found in tendons and ligaments o Characteristics: § Strong and durable § Contain protein collagen § Found in the intercellular materials of connective tissues · Elastic (yellow) fibers- found in vocal cords o Not as strong as white fibers, but more elastic 3 types of connective tissue cells · Fibroblast o Produce fibers found in the intercellular matrix (white and yellow) · Macrophage o Large phagocytic cells that clean up cellular debris and foreign particles · Mast cells o Contain heparin (anticoagulant) and histamine (promotes inflammation and activates allergies) Types of connective tissue · Loose (areolar) connective tissue o Characterized by loose network of collagenous and elastic fibers and a variety of connective tissue o Predominant cell is fibroblast § Fills the spaces in the body and binds together structures o Attaches skin to underlying muscles · Adipose tissue(fat)- protective cushion around organs o Specialized form of loose connective tissue in which there is very little intercellular matrix o Provides insulation and efficient energy storage material o Specialized for fat storage · Dense Fibrous connective tissue o Characterized by densely packed collagenous fibers in the matrix o Poor vascular supply o Forms tendons (connects muscle to bone) and ligaments (connects bone to bone) · Elastic connective tissue- closely packed elastic fibers o Yields easily to a pulling force then returns to its original length when force is released · Cartilage- has a matrix that contains the protein called chondrin and the cells called chondrocytes o Chondrocytes are located in the spaces called lacume o Cartilage is surrounded by a fibrous connective tissue membrane called perichondrium o Blood vessels don’t penetrate cartilage so cellular reproduction and healing occurs slowly · Hyaline cartilage- most common o Found at the end of long bones, trachea, costal cartilages and in the fetal skeleton · Fibro Cartilage- has an abundance of collagenous fibers and is found in intervertebral disks · Elastic Cartilage- has numerous elastic fibers in its matrix and is found in the framework of the external ear, epiglottis and auditory tubes. · Bone(osseous tissue)- rigid connective tissue with mineral salts, particularly calcium, giving it strength and hardness o Osteons and the haversian system are the structural units packed together to form the substance of compact bone o The center of the osteon is a tubular osteonic or haversian canal that contains a blood vessel and nerves o The bones matrix is formed in concentric circles/rings called lamellae o The microscopic channels in the bone provide a pathway for blood. The channels are called canaliculi o Oseocytes (bone cells) located in the lacunae are between the lamellae · Blood- has a liquid matrix called plasma o its cells are called Erythrocytes (RBC) which transport oxygen and Leukocytes (WBC) which fight disease o Thrombocytes (platelets) function in blood clotting 3. Muscle tissue- Made of cells that have the special ability to shorten, contract and produce movement · Has an abundance of cells and is highly vascular · Muscle cells are long and slender and are sometimes called muscle fibers and are arranged in bundles · Cell membrane is called sarcolemma and the cytoplasm is called sarcoplasm · The proteins actin and myosin are responsible for contraction and are found in the sarcoplasm 3 types of muscle tissue Skeleta-Smooth-Cardiac · Skeletal- cylindrical, multinucleated fibers with cross striations (series of straight lines) o The striations are produced by a pattern of actin and myosin o Comprises ~40% of body weight · Smooth Muscle Cells- spindle shaped o Contains 1 nucleus/cell o Lacks striations and is involuntary o Found in the calls of blood vessels and internal organs such as: § Stomach, intestines, bladder and uterus · Cardiac Muscle- has branching fibers, 1 nucleus/cell, striations and intercalated disks o Intercalated disk- where 1 cell attaches to another o Involuntary o Found in the call of the heart where it’s responsible for pumping blood through the heart and into the vessels 4. Nervous Tissue- · Found in the brain, spinal cord and nerves · Uses electrical nerve impulses to coordinate and control many bodily activities, stimulate muscle contractions, create awareness of the environment, play a role in emotions and memory and reasoning -Cells found in the nervous tissue: · Neurons- cells that generate and conduct electrical impulses o Have a cell body with efferent processes (carry impulses away) called axon o Have Aferrent process (toward body) called dendrites § Components of nerves: · Cell body- main part of the cell that carries general functions · Dendrites- extensions of cytoplasm that carry impulses to cell body · Axon- extensions that carry impulses away · Neuroglia- supporting cells of nervous tissues o Also called glial o Bind and insulate neurons o Some are phagocytic and protect against bacterial invasion o Others provide nutrients Inflammation and Tissue Repair · Inflammation- a nonspecific defense mechanism that attempts to localize or contain tissue injury and prepare the area for healing 4 manifestation: redness, swelling, heat and pain · Blood vessel dilation= redness and heat · Increased vascular permeability o Accumulation of fluid in the tissue puts pressure on nerves = pain and swelling · Inflammation is painful but beneficial o Cleansing of damaged area to prepare for repair and restoration · Tissue repair (regeneration and fibrosis) o Regeneration- replacement of destroyed tissue by cells that are identical to the original cells o Fibrosis- replacement of destroyed tissue by generation of fibrous connective tissue (scar tissue) § Most tissue repair is a combination of both Body membrane · Body membrane- thin sheet of connective tissue that covers the body, lines body cavities, covers organs and lines cavities in hollow organs Epithelial membranes and connective tissue membrane · Epithelial membranes are formed from epithelial tissue and the connective tissue to which it’s attached o Mucus and serous membranes · Connective tissue membranes contain only connective tissue o Synovial membrane and meninges Integumentary system- Subject to the most abuse Consists of: skin, hair and nails · Outer- epidermis · Inner dermis o Anchored to underlying tissues by the hypodermis Epidermis- made of stratified squamous epithelium · Because the epidermis is epithelium, it’s avascular. So cells receive their nutrients through diffusion from the vessels in the underlying tissue · In this skin, there are 5 distinct regions o Bottom layer- stratum basale § This is where melanocytes are found and hair is formed § Closest to blood supply · Melanocytes- specialized cells that produce melanin which gives hair, skin and eyes color § Melanocytes increase their production in response to sun exposure As new cells in the epidermis are produced, they’re pushed upward from the basement membrane toward the outside layer of the skin. They receive less nutrients the closer they are to the outside and die. As this process occurs; these cells undergo a hardening process called keratinization, where keratin is deposited in the cells · Keratin- water resistant protein that protects underlying cells o Next layer- stratum spinosum- superior to basale o Next layer- stratum granulosum- process of keratinization starts here o Next layer- stratum Lucidum- present only in thick skin § Thick skin- palm of hands and soles of feet o Next layer- stratum corneum- cells are continually shed and replaced § The outermost layer of epidermis It takes approx. 5 weeks for a cell to shed after being formed in the basale Skin Cancer- · Basal cell carcinoma- o Slow growing cancer that doesn’t metastasize. o Results from UV damage to the cells in the Basale o Cells multiply out of control o Looks like pink/pearly white bump · Squamous cell carcinoma- o Appears like ulcer/soar o Brought on by UV or exposure to carcinogens like tar and oil chemicals o Does metastasize · Malignant Melanoma o Caused from radiation damage to melanocytes o Has uncontrollable cell proliferation o May develop from existing mole o Fast growing o Tends to metastasize to: § Lung, liver and brain · Dermis- thicker than epidermis, also called stratum cornium o Composed of connective tissue embedded with blood vessels, nerves and accessory structures o Has collagenous and elastic fibers for strength and elasticity o If the skin is over stretched, the dermis can become damaged; leaving little white scars (stretch marks) called striae o Sensory receptors in the dermis detect changes in the environment such as heat, cold, pain, pressure and touch 2 layers of the dermis · Upper papillary layer o Papillae form ridges for grasping objects § basis for finger prints o small protrusions similar to a nipple that protrude from the dermal layer into the epidermal layer · Reticular layer- provides strength and resilience to stretch in many planes due to bundles of connective tissue fibers running in many different directions Supporting layer of skin · Hypodermis- subcutaneous layer/tissue anchors skin to underlying muscles o A connective tissue with a great abundance of adipose which acts as a cushion, heat insulator and energy source Skin Color 3 factors: 1. Melanin- basic skin color a. Produced by melanocytes in basale b. AKA dark pigment of skin 2. Carotene- pigment that gives a light yellow tint a. Can be due to eating a lot of yellow/orange veggies 3. Blood- blood in the dermal vessels give a pink color a. When we blush theres dilation of blood vessels in the dermis Accessory structures of the skin Hair, Nails, Sweat Glands and Sebaceous glands · Derived from stratum basale and are imbedded in reticular layer of the dermis Structure of hair and follicles · Central core of hair is the medulla and it’s surrounded by the cortex and cuticle o Hair is divided into the visible shaft and the root. The distal end of the hair follicle expands to form a bulb § The bulb is embedded in the reticular layer of the dermis o Stratum basale cells in the bulb undergo mitosis to create hair and increase length § Melanocytes produce melanin that determines hair color o Arrector pili muscle contracts in response to cold and/or fear making hair stand on end causing “goose bumps” o Cuticle is the outermost covering of the hair § Consists of overlapping keratinized cells 5 Epidermal Derivates cont… Nails: · Thin plates of keratinized stratum corneum. Each nail has 3 structures: · Free Edge o Part we can shape · Nail Body o Part you can see · Nail Root o Part that’s covered by edge Accessory structures · Eponychium o Fold of stratum corneum (cuticle) · Nail Bed o Formed by stratum basale and located under the nail body · Nail Matrix o Thickened region responsible for nail growth · Lanula o Portion of nail body that grows over the nail matrix Glands associated with the skin · Sebaceous glands - Oil glands o associated with hair follicles o Secrete Sebum (oil) § Sebum-helps keep hair and skin soft and pliable and helps prevent water loss(promotes moisture). Also inhibits bacterial growth. o Considered holocrine glands · Sudoriferous glands – Sweat Glands o Merocrine sweat glands - open to the surface of the skin through sweat pores and secrete perspiration in response to nerve stimulation and in response to heat. § Most numerous and widely distributed sweat glands o Apocrine sweat glands – larger than merocrine glands and their distribution is limited to the axillae and external genitalia where they open into hair follicles. § Become active at puberty and are stimulated in response to pain, emotional stress and sexual arousal o Ceruminous glands – modified sweat glands found only in the external auditory canal § Secrete cerumen (earwax) · Helps to repel insects and trap foreign material 4 functions of the skin 1. Protection- a. Protects from water loss, invading organisms, UV light and other injuries 2. Sensory reception- a. Sense receptors in the skin detect information about the environment i. Heat, cold, pain, touch and pressure 3. Regulation of body temperature- a. Constriction i. with vasoconstriction, blood flow decreases resulting in retention of body heat. 1. Skin looks pale because less blood reaches the surface b. Dilation i. With vasodilation, more blood passes through the capillaries near the skin surface resulting in body heat escaping by radiation 1. Skin looks red because more blood flow at surface a. Vasoconstriction/dilation = blood vessels constricting/dilating 4. Synthesis of Vitamin D- a. Precursors for Vitamin D are found in the skin. When they’re exposed to UV light, they are converted into active Vitamin D i. Vitamin D is required for calcium and phosphorous absorption in the small intestine 1. Calcium and phosphorous are essential for normal bone metabolism and muscle function Burns (figure 5-6 pg. 95) · 1st degree burns- o Superficial o Involve only the epidermis o Red and painful o And heal by regeneration · 2nd degree burns- o Partial thickness burns o Involve portion of the dermis o Form blisters o Painful and may produce scaring · 3rd degree burns- o Full thickness burns o Extend into subcutaneous tissue or below o White/charred in appearance o Cause no pain o Present problems with fluid loss and infection o Produce severe scarring · Rule of nines: · Used to estimate the amount of body surface area that’s burned · Each body region constitutes a % of the total that is multiple of 9 § Head and neck total 9% § each upper extremity is 9% § each lower limb is 18% § the entire trunk is 36% § the perineum is 1%