Tissues Flashcards
Functions of Epithelium tissue
Filtration
Absorption
Protection
Secretion
Special characteristics of Epithelium
- they have no blood supply of their own. Depend on diffusion of capillaries in underlying connective tissue for food and oxygen.
- regenerate themselves
- cells fit closely together to form sheets
- always have one unattached surface or edge. Apical surface is exposed to body’s exterior or the vacating of an internal organ.
- lower surface rests on a basement membrane
Tissues
Groups of cells that are similar in structure and function.
There are 4 primary tissue types.
What are the 4 primary tissue types?
Epithelium (covering)
Connective (support)
Muscle (movement)
Nervous (control)
Classifications of Epithelium
Simple Stratified Squamous Cuboidal Columnar
What is simple epithelium?
Absorption. Secretion, and filtration.
Very thin. NOT good at protection
- single layer of cells
- squamous or flat
- cuboidal or square
- columnar or rectangular
- pseudostratified columnar
Squamous simple epithelium
Single layer of thin squamous cells resting on a basement membrane. Fit closely together (floor tiles) and usually form membranes where filtration or exchange of substances by rapid diffusion occurs (air sacs of the lungs).
Also forms the serous membranes (the slick membranes that line the ventral body cavity and cover organs in that cavity)
Cuboidal or square simple epithelium
One layer of cuboidal cells resting on a basement membrane. Common in glands and their ducts (salivary gland, pancreas) and forms walls of the kidney tubules and covers the surface of the ovaries.
What is a basement membrane?
A structure less material secreted by the cells
Columnar or rectangular simple epithelium
Made of single layer of tall cells that fit closely together.
Goblet cells (produce lubricating mucus) often seen in this type of epithelium.
Lines the entire length of the digestive tract from stomach to anus.
What are mucosae or mucus membranes?
Epithelium membranes that line body cavities open to the body exterior
Pseudostratified Columnar simple Epithelium
All of the cells rest on a basement membrane but some are shorter than others and their nuclei appear at different heights above the basement membrane. As a result, this epithelium gives a false impression that it is stratified.
Mainly functions in absorption and secretion like simple columnar epithelium.
A ciliated variety lines most of the respiratory tract. The mucus produced by goblet cells in the epithelium traps dust and debris and the cilia propel the mucus upward and away from the lungs.
Stratified epithelium
- forms 2 or more layers
- more durable than the simple epithelia
- primarily to protect
- squamous or flat
Most common epithelium in the body. Consists of several layers.
Stratified Squamous epithelium
Stratified epithelium cells consist of many layers of cells. The cells at the free edge are the squamous cells.
Stratified squamous epithelium cells are found in sites that receive a good deal of abuse or friction such as the esophagus, mouth, and outer portion of the skin.
Stratified Cuboidal Epithelium
Usually has just 2 cell layers with the surface being cuboidal (square) in shape.
Found mainly in the ducts of large glands
Fairly rare in the body
Stratified Columnar Epithelium
The surface cells of stratified columnar epithelium are columnar cells but it’s basal cells vary in size and shape.
Fairly rare in the body, being found mainly in the ducts of large glands.
Psuedostratified Columnar or Transitional Epithelium
Highly modified, stratified squamous epithelium that forms the lining of only a few organ (urinary bladder, ureters, part of urethra -all part of urinary system and subject to stretching).
When the organ is distended with urine, the epithelium thins and cells flatten and become squamous like to allow more urine to be stored.
Epithelium tissue
The lining, covering, and glandular tissue of the body.
One type forms the outer layer of the skin, others dip into the body to line it’s cavities
Forms the boundaries that separate us from the outside world
Stratified Glandular Epithelium
A gland that consists of one or more cells that make and secrete a particular product (secretion) that contains protein molecules in a water based fluid.
2 major types of glands developed from epithelium sheets:
Endocrine
Exocrine
What are Endocrine glands?
Endocrine glands lose their connection to the surface (duct) and are often called ductless glands. Secrete all hormones and diffuse directly into the blood vessels that weave through glands. Ex: thyroid, adrenals, pituitary
What are Exocrine glands?
Exocrine glands retain their ducts and their secretions empty through the ducts to the epithelial surface. They include sweat & oil glands, liver, and pancreas (both internal and external)
Connective tissue
It connects body parts and is found everywhere in the body. Most abundant and widely distributed of the tissue types.
Most connective tissue is well vascularized, but there are exceptions (tendons & ligaments have poor blood supply and cartilages are avascular so they heal slowly when injured).
Extracellular matrix (made of many different types of cells plus varying amounts of no living substances found outside the cells)
Primarily involved in protecting, supporting, and binding together other body tissues.
What is an Extracellular matrix?
Connective tissues made up of many different types of cells plus varying amounts of non living substances found outside the cells.
Matrix is produced by CT cells and then secreted to their exterior. Depending on CT type, may be liquid, semisolid, gel like, or very hard. Able to bear weight, stretch, and withstand other abuses that no other tissue could endure.
Bone has very few cells and large amounts of hard matrix whereas fat has many cells and the matrix is soft.
Various types and amounts of fibers are deposited and form a part of the matrix material. They include collagen (white), elastic (yellow), and reticular (fine collagen) fibers like the rest of the matrix. The fibers are made by CT cells and then secreted.
Types of Connective Tissue (CT)
All CT consists of living cells surrounded by a matrix.
Bone
Areolar tissue
Loose CT
Dense CR
Cartilage
Reticular CT
Adipose tissue
Blood
Bone
Type of CT
Sometimes called osseous tissue and is composed of bone cells sitting in vagaries called lacunae and surrounded by layers of very hard matrix that contain calcium salts in addition to large numbers of collagen fibers.
Protect and supports other body organs
Cartilage
Type of CT
Less hard and more flexible than bone.
Most widespread is hyaline cartilage, which has abundant collagen fibers hidden by a rubbery matrix with a glossy blue-white appearance. Forms the supporting structures of the larynx, attaches the ribs to the breastbone and covers the ends of the bones with hyaline cartilage.
Hyaline is the most widespread but there are also
Elastic Cartilage (found where structures need elasticity ex: Ear)
Fibrocartilage (highly compressible. Forms on cushion like disks between vertebrae of the spinal column)
Dense CT
Type of CT
Also called Denae fibrous tissue. Has collagen fibers as its main matrix element. Crowded between the collagen fibers are rows of fibroblast that make the fibers.
Forms strong rope like structures like tendons and ligaments
Ligament fibers contain more elastic fibers than tendons.
Makes up lower layers of the skin where it’s arranged in sheets.
Loose CT
Type of CT
Softer and have more cells and fewer fibers than any other CT type except blood.
Areolar tissue
Most widely distributed CT in the body, is soft, pliable tissue that cushions and protects the body organs it wraps.
Functions a universal packing tissue and CT ‘glue’ (helps hold the internal organs together)
Lamia propria underlies all mucous membranes
Fluid Matrix forms a loose network and mostly looks empty on a microscope (explains name areola = small open space)
Provides a reservoir of water and salts for surrounding tissues and all body cells obtain their nutrients from and release their wastes into this tissue fluid.
Soaks up excess fluid like a sponge when a region is inflamed (area becomes puffy and swells called Edema)
Adipose tissue
Aka Fat
Areolar tissue in which fat cells predominate.
Fat cells often called signet ring cells
Droplet of oil accompanies fat cell and causes nucleus to displace to one side through compression.
Forms subcutaneous tissue beneath skin where it insulates the body and protects it from heat and cold extremes.
Protects individual organs like kidneys and cushions eye balls.
Fat deposits are available for fuel (hips and breasts)
Reticular CT
Consists of delicate network of interwoven reticular fibers associated with reticular cells which resemble fibroblasts.
Limited to certain sites.
Forms a stroma (bed, mattress) or internal supportive framework which supports free blood cells in lymphoid organs such as lymph nodes, spleen, and bone marrow.
Blood
Type of CT
Vascular tissue
Considered a CT because it consists of blood cells surrounded by a no living fluid matrix called blood plasma.
Blood fibers are soluble protein molecules that become visible only during blood clotting.
Blood is the transport vehicle for the cardiovascular system, carrying nutrients, wastes, respiratory gases, and many other substances throughout the body.
Muscle tissue
Highly specialized to contract or shorten to produce movement. Because muscle cells are elongated to provide a long axis for contraction they are called muscle fibers
Types of muscle tissue:
Skeletal
Cardiac
Smooth muscle (visceral muscle)
Skeletal muscle
Packaged by CT sheets into organs which are connected to the skeleton.
Can be controlled voluntarily or consciously and form the flesh of the body.
Cells are long, cylindrical, and multinucleate (they have obvious straitions)
Cardiac muscle
Found only in the heart
As muscle contracts, heart acts as a pump and propels blood through the blood vessels.
Has straitions
Cells are unnucleated that fit closely together at junctions called intercalated disks. These gap junctions that allow ions to pass freely from cell to cell resulting in rapid conduction of exciting electrical impulse across the heart.
Involuntary
Smooth (Visceral) muscle
No straitions are visible
Single nucleus and are spindle shaped (pointed at each end)
Found in walls of hollow organs such as stomach, bladder, uterus, and blood vessels.
When contracted, cavity of an organ alternately becomes smaller (contracts) or enlarges (dilates) so the substances are propelled through the organ along a specific pathway.
Contracts more slowly than the other two muscle types.
Peristalsis is typical of its activity (wave like motion that keeps foots moving through small intestine).
Nervous tissue
All neurons receive and conduct electrochemical impulses from one part of the body to another.
2 major functional characteristics:
Irritability and conductivity
What allows a single neuron to conduct an implies over a long distance in the body?
The cytoplasm is drawn into long extensions (as much as 3’ in the human leg).
Neurons along with a special group of supporting cells that insulate the structures of the nervous system the brain, spinal cord, and nerves.
Tissue repair
Intact physical barriers (skin & mucous membranes, cilia, and the strong acid produce by stomach glands) are 3 examples of body defended exerted at the local tissue level.
Healing process starts almost immediate after an injury.
Inflammation is a generalized body response that attempts to prevent further injury.
Immune response is extremely specific and mounts a vigorous attack against invaders.
Tissue repair occurs in 2 major ways:
Regeneration
Fibrosis
Occurrence depends on the type of damage and the severity of the injury.
Sets a serious of events into motion in the healing process.
Regeneration tissue repair
The replacement of destroyed tissue by the same kind of cells
Fibrosis tissue repair
Involves repair by defense (fibrous) connective tissue by the formation of scar tissue.
First step in tissue repair
Capillaries become permeable which allows fluid rich in clotting proteins and other substances to come into injured area to clot.
This stops loss of blood, holds the edges of the wound together and effectively ‘walls off’ the injured area, preventing bacteria spreading into surrounding tissues.
When clot exposed to air it gets hard and forms scab.
Second phase of tissue repair
Granulated tissue forms (pink delicate tissue composed of capillaries) into damaged area from undamaged blood vessels nearby. Fragile and bleed freely when scab is picked.(proud flesh)
Granulated tissue contains phagocytes that dispose of the blood clot and CT cells (fibroblasts)that synthesize collagen fibers (scar tissue) to permanently bridge the gap.
Final step of tissue repair
Surface epithelium begins to regenerate and make its way across granulation tissue beneath scab which soon detaches.
Final result is a fully regenerated surface epithelium that covers scar. Scar is invisible or visible depending severity of wound.
Scarring depends on people’s race & horse’s breed. QHs have a lot of muscle and thicker skin to protect it so they scar bigger than TBs who scar flat and small.
How do the different tissue types regenerate?
Epithelium tissues (skin, mucus membranes) regenerate beautifully just like fibrous CT and bone.
Skeletal muscle regenerates poorly if at all
Cardiac muscle and nervous tissue within the brain and spinal cord are replaced only by scar tissue.
Scar tissue is strong but lacks flexibility and is unable to perform normal functions of the tissue it replaces. If scar tissue covers a bladder, heart, or another muscular organ, it may severely hamper the function of that organ.
