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What are the 4 general types of tissue in the human body?
Epithelial, connective, nervous, and muscles
What is epithelial tissue and where is it usually found?
Protective covering of external and internal body surfaces. Mostly cells, very little extracellular matrix.
What are the 3 surfaces found on most epithelial tissue?
- 1) Free or apical surface: not attached to any other cells
- 2) Lateral surface: attached to adjacent cells
- 3) Basal surface: attached to basement membrane
What is the basement membrane?
Meshwork of proteins secreted by epithelial cells and underlying connective tissue. "Like adhesive on tape"
What are the roles of the basement membrane?
- 1) guiding and supporting cell migration during tissue repair
- 2) help attach epithelial cells to underlying tissue
How do epithelial cells exchange gas and nutrients?
Epithelial cells are avascular, so they exchange gas and nutrients through diffusion with blood vessels in underlying tissue.
What are 5 basic functions of epithelial tissue?
- 1) Protection of underlying structures
- 2) Acting as barriers
- 3) Allowing passages of certain substances
- 4) Secreting substances
- 5) Absorbing substances
What are simple and stratified epithelium?
- Simple: 1 layer of cells
- Stratified: Multiple layers of cells
What are the different shapes of epithelial cells?
- 1) Squamous (Flat, thin)
- 2) Cuboidal
- 3) Columnar
What is simple squamous epithelium and where is it typically found?
Single layer of flat, thin cells.
Often found where diffusion/filtration occur (alveoli, glomerulus, blood vessels, serous membranes, and inner ear drums).
Coat organs and lubricated to decrease friction.
What is simple cuboidal epithelium and where is it typically found?
Single layer of cuboidal cells, some w/microvillia (kidney tubules) or cilia (terminal bronchioles)
Found in areas of active transport and facilitated diffusion.
Secretion and movement of mucous.
What is simple columnar epithelium and where is it typically found?
Single layer of tall, narrow cells
Some have cilia (bronchioles, auditory tubes, uterine)
Some have microvilli (intestines)
What is pseudostratified columnar epithelium and where is it typically found?
Single layer of cells with differing heights, giving the appearance of multiple layers.
Synthesize and secrete mucous, move mucous and fluid away from passages (nasal cavity, sinuses, pharynx, trachea, auditory tubes, bronchi)
What is stratified epithelium?
several layers of cells, deepest cells are cuboidal or columnar and capable of dividing and producing new cells.
As new cells are pushed to the surface, they flaten. If cells at surface are damaged or rubbed away, new cells replace them.
What is stratified squamous epithelium? What are the two types?
- Cuboidal basal layer, squamous at surface.
- 1) nonkeratinized (moist)
- 2) keratinized
Nonkeratinized squamous epithelium
Surface cells in this tissue retain a nucleus and organelles.
Found in mouth, throat, larynx, esophagus, anus, vagina, inferior urethra and cornea. (Anywhere that may experience a lot of abrasion)
Keratinized squamous epithelium
Surface cells are dead, cytoplasms are replaced with keratin protein. Found in skin.
What is stratified cuboidal epithelium? Where is it found?
Multiple layers of cuboidal cells. Found in areas where secretion, absorption, protection vs infection.
Sweat gland ducts, ovarian follicles, salivary gland ducts.
What is stratified columnar epithelium?
Layers of columnar cells on top of cuboidal cells. Protection and secretion.
Mammary gland ducts, larynx, part of male urethra.
Cells look cuboidal or columnar when organ or tube is not stretched. Cells look squamous when stretched.
Stretches with change in volume, protects against caustic effects of urine. Lining of urinary bladder, ureters, and superior urethra.
What is the primary function of simple epithelium?
Move materials (gas and fluids)
What is the primary function of stratified epithelium?
Well adapted for protection
What is the primary function of stratified squamous epithelium?
Areas where abrasion occur.
Function of simple squamous cells?
Diffusion (ie. alveoli)
Function of cuboidal or columnar cells?
Since they are larger with more organelles, they are better for secretion or absorption.
Types of free or apical surface and their function?
- Smooth: reduce friction (ie. blood vessels)
- Microvilli: increase surface area for absorption and secretion.
- Cilia: propel materials along surface of cells
What are tight junctions?
Permeability barriers that wrap around each cell forcing things to go through the cell. The cell is selective due to plasma membrane.
What are desmosomes? What about hemidesmosomes?
mechanical links that bind cells together
anchor cells to basement membrane
What are gap junctions?
Small protein channels that allow small molecules and ions to pass from cell to cell.
What are glands?
Multicellular, secretory structures made of epithelial tissue and supporting connective tissue.
What are the two types of glands? What is the main difference between them?
Endocrine: release hormones into the bloodstream. Affect distant things.
Exocrine: release things out of body through DUCTS! Sweat, saliva, oil
What are the 3 types of exocrine glands?
- 1) Merocrine
- 2) Apocrine
- 3) Holocrine
What are merocrine glands?
Excretory glands that secrete products without loss of cellular matrix. Simple things like sweat, exocrine pancreas.
What are apocrine glands?
Discharge fragments of gland cells in secretions. Ie. milk produced in mammary glands
What are holocrine glands?
Shed entire cells, products accumulate in cytoplasm of cells until they rupture.
Ie. Sebaceous glands of skin
What are the different types of glands based on the duct system?
- Simple: 1 duct
- Compound: Branching, multiple ducts
- Acini: small grape clusters of ducts (sebaceous glands)
- Alveoli: Hollow sacs
What are the 7 functions of connective tissue?
- 1) Enclosing and separating
- 2) Connect different tissue (tendons=muscle to bone, ligaments= bone to bone)
- 3) Supporting and moving
- 4) Storage (Fat and minerals)
- 5) Cushioning and insulation (Fat)
- 6) Transporting (blood)
- 7) Protection (Bones, immune cells)
How much extracellular matrix does connective tissue have compared to epithelial tissue?
Abundant extracellular matrix, epithelial has very little.
What are mast cells?
Non-motile cells that release chemicals (histamine) that promote inflammation.
What are the 3 types of protein fibers that help form connective tissue?
- 1) Collagen fibers
- 2) Reticular fibers
- 3) Elastic fibers
What is collagen fiber?
microscopic ropes, flexible, but resist stretching
What is reticular fiber?
Very fine, short collagen fibers that branch to form a supporting network
What is elastic fiber?
similar to bed springs, after being stretched, they can return to original shape
What is ground substance?
Shapeless background which cells and collagen fibers are seen on microscope. Looks shapeless, but highly structured.
What are proteoglycans?
Mixture of proteins and polysaccharides. Like pine tree limbs: Branches= protein, needles= polysaccharides.
They are able to hold lots of water b/w polysaccharide molecules and return to normal shape after compression and deformation
What is mesenchyme?
Embryonic connective tissue made out of irregular shaped fibroblasts surrounded by abundant, semifluid extracellular matrix where delicate collagen fibers are distributed.
All adult tissue develops from mesenchyme.
When does mesenchyme form?
3-4 weeks into fetal development from mesoderm and neural crest cells.
By 8 weeks it has specialized into the 6 types of connective tissue
What are the 6 types of connective tissue?
- 1) Mesenchyme
- 2) Loose (areolar) connective tissue
- 3) Dense connective tissue
- 4) Special purpose connective tissue
- 5) Cartilage
- 6) Bone
- 7) blood and hemopoietic tissue (marrow)
What is the structure of loose connective tissue?
Mostly collagen, some elastic fibers, spaces filled with fibroblasts, macrophages, and lymphocytes
What is the function of loose connective tissue? Where is it found?
Loose packing, support, nourishment for structures associated with it.
All over the body, it is what the basement membrane rests on. It attaches skin to underlying tissue.
What are the 4 types of dense connective tissue?
- 1) Regular collagenous
- 2) Regular elastic
- 3) Irregular collagenous
- 4) Irregular elastic
What is the structure of regular collagenous dense connective tissue?
Matrix made of collagen fibers running in about the same direction.
What is the function of regular collagenous dense connective tissue?
Able to withstand great pulling forces in direction of fiber orientation. Great tensile strength and stretch resistance.
Found in tendons (muscle to bone) and ligaments (bone to bone)
What is the structure of regular elastic dense connective tissue?
Regularly arranged collagen and elastin fibers.
What is the function of regular elastic dense connective tissue?
Able to stretch and recoil in direction of fiber orientation.
Found in vocal folds, elastic ligaments b/w vertebrae and along dorsal aspect of neck.
What is the structure of irregular collagenous dense connective tissue?
Collagen fibers oriented in all directions or alternating planes of 1 direction orientation.
What is the function of irregular collagenous dense connective tissue?
Tensile strength capable of withstanding stretching in many directions. Found in sheaths, most of dermis, organ capsules and septa, outer covering of body tubes.
What is the structure of irregular elastic dense connective tissue?
Bundles and sheets of collagen and elastin fibers oriented in multiple directions.
What is the function of irregular elastic dense connective tissue?
Capable of strength with stretching and recoil in many directions
Found in elastic arteries.
Connective tissue with special properties
- 1) Adipose tissue
- 2) Reticular tissue
Adipose tissue structure and function
Little extracellular matrix, so full of lipid, cytoplasm pushed to periphery of cell
Insulation, energy storage, protection of organs
Subcutaneous areas, yellow marrow, mesenteries.
Structure of Reticular tissue
Fine network of reticular fibers, irregularly arranged
What is the function of reticular tissue?
Provides a superstructure for lymphatic and hemopoietic tissues.
Found within lymph nodes, spleen, and bone marrow
What are the 3 types of cartilage?
- 1) Hyaline cartilage
- 2) Fibrocartilage
- 3) Elastic cartilage
What is the structure of hyaline cartilage?
Collagen fibers are small and evenly dispersed, seems almost transparent. Chondrocytes found in lacunae (spaces) within matrix.
What is the function of hyaline cartilage?
Allows growth of long bones, provides rigidity with some flexibility (trachea, bronchi, ribs, and nose).
Forms rugged, yet somewhat smooth articulating surfaces and also forms embryonic skeleton.
Where is hyaline cartilage found?
Growing long bones (epiphyseal plate), cartilage rings of respiratory system, costal cartilage, nasal, articulating surfaces of bones.
What is the structure of fibrocartilage?
More collagen than hyaline, thick bundles
What is the function of fibrocartilage?
Somewhat flexible, able to withstand great pressure. Connects structures that are subject to great pressure.
Where is fibrocartilage found?
Intervertebral disks, symphysis pubis, articular disks (knee and temporomandibular joint (TMJ))
What is the structure of elastic cartilage?
Similar to hyaline, with small evenly dispersed collagen fibers, but also contains elastic fibers.
What is the function of elastic cartilage?
Rigidity with more flexibility than hyaline cartilage due to elastic fibers.
Found in external ears, epiglottis, and auditory tubes.
What is inflammation?
A response to tissue damage from physical, biological, or chemical sources.
What are the main mediators of inflammation?
Chemicals that promote inflammation in injured or infected tissue
Histamine, kinins, prostaglandins, and leukotrines.
What are the 5 major symptoms of inflammation?
- 1) Erythema
- 2) Heat
- 3) Swelling
- 4) Pain
- 5) Disturbance of function
What causes erythema?
Dilation of blood vessels in the area, brings more blood resulting in red color. More blood needed to bring immune cells to fight infection.
What causes swelling from inflammation?
Increased permeability of blood vessels due to increase need of blood cells and immune cells to move into tissues to fight infection. Water follows the proteins that move into tissue causing edema.
Why is chronic inflammation bad?
It can cause normal tissue to be replaced by connective tissue resulting in a loss of function.
What are labile cells?
Cells that continue to divide throughout life.
Ie. skin, mucous membranes, hemopoietic and lymphatic tissue.
Damage to cells repaired by regeneration of the same cells.
What are stable cells?
Cells that don't actively divide after growth ends but can regenerate after injury.
Connective tissue, glands, liver, pancreas, smooth muscle.
What are permanent cells?
Cells that have little or no ability to divide. Usually replaced by connective tissue which results in decrease of function.
Neurons, skeletal and cardiac muscles.
What are the 8 steps in wound healing?
- 1) Edges of wound close together and wound fills with blood
- 2) A clot is formed by fibrin which holds wound together and hemostasis is acheived
- 3) Surface of clot dries to form scab
- 4) Inflammatory response is activated (blood vessel dilation and permeability)
- 5) Neutrophils and macrophages phagocytize bacteria and die forming pus (dead cells and fluid)
- 6) Macrophages remove dead cells and decompose clot
- 7) Granulation tissue forms, contains fibroblasts that make collagen and capillaries to revascularize the area (large amount of granulation tissue forms scar tissue)
- 8) Granulation tissue replaced by dermis, scar turns from red to white as collagen replaces blood vessels.