UNIT 4 T I S S U E S

WHAT IS A TISSUE Group of cells that work together to do a function Cells are similar Extracellular fluid around them is similar Histology

EPITHELIAL TISSUE Also called epithelium Covers internal and external surfaces throughout body There is usually very little extracellular material between cells Most have a free surface and a basal surface Basal surface attaches to the basement membrane

BASEMENT MEMBRANE Secreted by epithelial cells and cells of underlying tissues Attaches epithelial cells to other tissues Made of proteins and other molecules Blood vessels do not cross the basement membrane

FUNCTIONS OF EPITHELIAL TISSUE Protecting underlying structures Acting as a barrier Permitting the passage of substances Secreting substances Absorbing substances

CLASSIFICATION OF EPITHELIAL TISSUE Simple vs Stratified Shape classification Squamous Cuboidal Columnar Names by the number of layers and shape Stratified are named by shape of cells on free surface

SIMPLE SQUAMOUS EPITHELIUM One layer of flat cells Often have a hexagon shape Controls materials that move from one part of a body to another Prevents abrasion Locations: line blood vessels, heart, lymphatic vessels, alveoli of lungs, portions of kidney tubules, line serous membranes

SIMPLE SQUAMOUS EPITHELIUM

SIMPLE CUBOIDAL EPITHELIUM One layer of cube-like cells May have microvilli or cilia Do active transport, facilitated diffusion, and secretion Locations: Kidney tubules, glands and their ducts, lining of bronchioles, surfaces of ovaries

SIMPLE CUBOIDAL EPITHELIUM

SIMPLE COLUMNAR EPITHELIUM One layer of tall, thin cells Perform complex functions, movement, and secretion May have cilia or microvilli Some cells are goblet and produce mucus Locations: Lungs, fallopian tubes, stomach, intestines, auditory tubes, glands and some of their ducts, part of the brain

SIMPLE COLUMNAR EPITHELIUM

PSEUDOSTRATIFIED COLUMNAR EPITHELIUM One layer of cells that looks like two and usually have cilia Some are tall enough to reach the free surface while others are not nuclei are at different levels and this gives the appearance of being stratified. Many cells are goblet and produce mucus Secrete mucus and use cilia to move it or other fluid over the free surface Locations: Lining of nasal cavity, nasal sinuses, auditory tubes, pharynx, trachea, and bronchi

PSEUDOSTRATIFIED COLUMNAR EPITHELIUM

PSEUDOSTRATIFIED COLUMNAR EPITHELIUM WITH GOBLET CELLS

STRATIFIED SQUAMOUS EPITHELIUM Thick layer of cells Cells close to the basement membrane are cuboidal or columnar These can divide to produce new cells Some of these move away from the basement membrane These become flat These often form protective layers Keratinized Locations: Outer layer of skin Nonkeratinized Locations: Mouth, throat, larynx, esophagus, anus, vagina, urethra, and cornea

STRATIFIED SQUAMOUS EPITHELIUM

STRATIFIED CUBOIDAL EPITHELIUM More than one layer (stratified) of cuboidal epithelial cells Functions are absorption, secretion, and protection Locations (rare) : sweat gland ducts, ovarian follicular cells and salivary glands

STRATIFIED CUBOIDAL EPITHELIUM

STRATIFIED COLUMNAR EPITHELIUM Consists of more than one layer of epithelial cells Only the surface cells are columnar Deeper layers are irregular or cuboidal shape Functions are secretion and protection. Locations (rare): mammary gland ducts, larynx, male urethra

STRATIFIED COLUMNAR EPITHELIUM

TRANSITIONAL EPITHELIUM Special type of stratified epithelium that can be greatly stretched Unstretched 5 or more layers of cuboidal or columnar cells that are often dome shaped Stretched low cuboidal or squamous shaped and the number of cell layers decreases Functions are to accommodate fluctuations in volume of organs. Locations: bladder, stomach

TRANSITIONAL EPITHELIUM

STRUCTURE AND FUNCTION Two ways that epithelial tissues are classified or defined Structure is how something is made how many layers and what sort of shape Function is what something does

STRUCTURE AND FUNCTION CELL LAYERS Simple (one layer) is primarily found in organs that move materials Examples include alveoli in the lungs, filtration of fluid across filtration membranes in the kidneys, and nutrient absorption by the intestines.

STRUCTURE AND FUNCTION CELL SHAPE Differences in function are reflected in cell shape Flat and thin Cuboidal or columnar

STRUCTURE AND FUNCTION EFFECTS OF IRRITATION Shape and number of layers can change in response to irritation

STRUCTURE AND FUNCTION

STRUCTURE AND FUNCTION FREE SURFACES Smooth reduces friction Microvilli common if function is absorption Cilia common if function is to move material across cell surface Goblet cells secrete mucus

STRUCTURE AND FUNCTION FREE SURFACES

STRUCTURE AND FUNCTION FREE SURFACE

STRUCTURE AND FUNCTION CELL CONNECTIONS Tight junctions attach to neighboring cells Desmosomes mechanical connections between cells Hemidesmosome hold cell to basement membrane Gap Junctions Tunnels between neighboring cells

STRUCTURE AND FUNCTION CELL CONNECTIONS

GLANDS Secretes substances onto a surface, into a cavity, or into the blood Unicellular glands

GLANDS Exocrine glands substance is secreted onto a surface or into an organ Simple vs compound Tubular vs Acinus/Alveolus Tubuloacinar or tubuloalveolar

GLANDS

GLANDS Endocrine glands hormones are secreted into blood Examples: Thyroid gland, Insulinsecreting portions of the pancreas

CONNECTIVE TISSUE A lot of extracellular material between cells AKA extracellular matrix Made of protein fibers, ground substance, and fluid

PROTEIN FIBERS OF EXTRACELLULAR MATRIX Collagen Fibers Reticular Fibers Elastic Fibers

GROUND SUBSTANCE Cells and protein fibers are in this Contains proteoglycans Trap water

NAMING OF CONNECTIVE TISSUE CELLS Suffix is determined by function blast cyte clast

IMMUNE SYSTEM Cells involved in the immune response are found in connective tissue Macrophages Mast Cells

FUNCTIONS OF CONNECTIVE TISSUE Enclosing and separating other tissues Connecting tissues to one another Supporting and moving parts of the body Storing compounds Cushioning and insulating Transporting Protecting

CLASSIFICATION OF CONNECTIVE TISSUE 6 types develop during embryonic development Loose (areolar), Adipose tissue, Dense connective tissue, Cartilage, Bone, and Blood Extracellular matrix is mostly responsible for function in each of these types

LOOSE CONNECTIVE TISSUE AKA Areolar Structure Mostly collagen with a few elastic fibers for extracellular matrix Fibroblasts Locations: throughout body especially between glands, muscles, and nerves Functions: packing material, attaches skin to underlying tissues

ADIPOSE TISSUE Structure collagen and elastic fibers in extracellular matrix Very little extracellular matrix Function store energy, padding/protection, insulation, packing material Locations: Under skin, mesenteries, around kidneys, surface of colon, mammary glands, in loose connective tissue found in spaces/crevices

DENSE CONNECTIVE TISSUE Extracellular matrix has densely packed fibers made by fibroblasts Dense Collagenous Connective Tissue Structure: Extracellular matrix is mostly collagen fibers Fibers may run in same or different directions Function: Withstand great pulling forces, attach body parts Locations: Tendons, ligaments, skin, organ capsules, outer layer of blood vessels

DENSE CONNECTIVE TISSUES Dense Elastic Connective Tissue Structure: Elastic fibers mixed in with collagen fibers Fibers may run in same or different directions Function: Stretch and recoil Locations: Elastic ligaments (between vertebrae of neck), vocal cords, walls of arteries

CARTILAGE Structure: made of chondrocytes in lacunae Lot of extracellular matrix with collagen Can spring back after being compressed Hard to repair Three types Hyaline cartilage Fibrocartilage Elastic cartilage

Hyaline Cartilage Structure: Small collagen fibers that are evenly dispersed in matrix Functions: Forms embryonic skeleton, covers joints and is smooth but withstands compression, allows growth of long bones, provides rigid structures that have some flexibility Locations: Long bones, trachea, nose, joints, costal cartilage

Fibrocartilage Structure: More collagen that is in bundles Functions: Withstand greater pressure but is a little flexible Locations: Spine, knee, jaw

Elastic Cartilage Structure: Collage is small and evenly dispersed but matrix also contains elastic fibers Functions: Provide structure but are more flexible and can go back to original shape Locations: External ear, epiglottis, auditory tubes

Bone Structure: Mineralized matrix with cells in lacunae Function: Strength, rigidity, protection, movement, storage Location: Throughout body

Blood Structure: Liquid matrix Function: Transportation, homeostasis, immunity Location: Blood vessels, white blood cells may enter other tissues

Muscle Tissue Function: Contraction to allow movement Structure: Contractile proteins in muscle cells, length greater than diameter Three types: Skeletal, Cardiac, and Smooth

Skeletal Muscle Function: Movement usually voluntary Structure: Long, cylindrical, several nuclei per cell, striated Location: Attached to bones or other connective tissue

SKELETAL MUSCLE

Cardiac Muscle Function: Pumps blood involuntary Structure: Short, cylindrical, one nucleus per cell, striated, branched, connected to each other with intercalcated disks Location: Heart

CARDIAC MUSCLE

Smooth Muscle Functions: Regulates size of organs, forces fluid through tubes, controls amount of light going into the eye, homeostasis Structure: Not striated, tapered at each end, one nucleus Locations: Hollow organs (except heart), eye, skin

SMOOTH MUSCLE

COMPARING MUSCLE TYPES

Nervous Tissue Location: brain, spinal cord, nerves Function: Coordinate and control body activities, awareness, emotions, thinking, memory Structure: Contains cell body, dendrite, and axon Neuroglia are support cells that insulate, nourish, and protect neurons

NEURON

Membranes Thin sheet or tissue that covers a structure or lines a cavity Structure: epithelium resting on connective tissue Found externally and internally

External Membrane Skin Structure: stratified squamous epithelium on dense connective tissue

Mucous Membranes Internal membrane Structure: epithelium on a thick layer of loose connective tissue, most have mucous glands Location: Cavities that open to outside of body Functions: protection, absorption, secretion

Serous Membranes Structure: simple squamous epithelium on thin layer of loose connective tissue Location: Line body trunk cavities and cover organs within Functions: Produce serous fluid, lubrication, prevent abrasion

Synovial Membranes Structure: only connective tissue Location: Line joint cavities Function: Produce synovial fluid

Tissue Damage and Inflammation Inflammation can be caused by tissue damage Function of inflammation: mobilize body defenses, isolate and destroy pathogens and dead cells Symptoms of inflammation: redness, heat, swelling, pain, disturbance of function

How Inflammation Occurs Injury Chemical mediators are released/activated Membranes of blood vessels become more permeable Edema Isolation of site Neutrophil Pus

Pain from Inflammation Due to Damage to nerves Chemical mediators Increased pressure due to edema and pus Beneficial because may cause patient to take better care of themselves and prevent further injury

Chronic Inflammation Due to interference with healing process, cause of injury not being removed, prolonged exposure to irritants, abnormal immune response May cause normal tissue to be replaced by fibrous connective tissue Can cause organs to no longer function properly Treatments may provide relief

Tissue Repair Substitution of living cells for dead cells Regeneration vs Replacement

Response to Wounds Clot Bleeding stops Scab Inflammatory response Isolation Regeneration of epithelium at edge of wound Scab falls off after new epithelium from each side of would meets Macrophage clears dead cells, debris, and clot Fibroblasts produce extracellular matrix Revascularization Granulation tissue replaces clot Normal connective tissue replaces granulation tissue

Effects of Aging on Tissues Cells divide more slowly Tissue repair is slower Reduced number of neurons and muscle cells Collagen fibers become more irregular in structure Elastic fibers fragment Atherosclerosis

CELL TYPES Permanent cells Labile cells Stable cells