Chapter 4: Tissues Flashcards
Where are epithelial tissues located?
Covers body surfaces
Lines body cavities
Hollow organs and ducts
Forms glands
What does connective tissue do?
This protects and supports the body and its organs
Binds organs together
Stores energy reserves as fat
Provides immunity
What does muscular tissue do?
This generates physical force needed to make body structures move
What does nervous tissue do?
This detects changes inside and outside the body and initiates and transmits nerve impulses that coordinate body activities to help maintain homeostasis
What are cell junctions?
These are the points of contact between most epithelial cells and some muscle and nerve cells, tightly joining them into functional units
What are the two main types of epithelial tissue?
Surface epithelium (aka covering and lining epithelium)
Glandular epithelium
Where is surface epithelium located?
Outer covering of the skin and some internal organs
Lines body cavities, blood vessels, ducts, and interiors of the respiratory, digestive, urinary, and reproductive systems
Makes up parts of the organs for hearing, vision, and touch.
Where is glandular epithelium located?
Makes up secreting portion of glands like sweat, thyroid, adrenal, and digestive glands
What are the general features of epithelium?
Mostly or entirely made up of closely packed cells with little extracellular material between them
Arranged in continuous sheets
Have an apical (free) surface, lateral surface, and basal surface
Avascular
Has a nerve supply
High capacity for renewal by cell division
What is the apical surface of epithelium?
This is the surface exposed to a body cavity, lining of an internal organ, or the exterior of the body.
For epithelia with multiple layers, this is the most superficial layer
What is the lateral surface of epithelium?
This is the surface that faces adjacent cells
What is the basal surface of epithelium?
This is the surface that attaches to a basement membrane. For epithelia with multiple layers, this is the deepest layer
What is a basement membrane?
This is a thin extracellular structure made mostly of protein fibers. It acts as an anchor between epithelial tissue and its underlying connective tissue
How are basement membranes affected in diabetes mellitus?
In untreated cases, basement membranes of capillaries can thicken especially in the eyes and kidneys, leading to blindness and kidney failure
What are the 3 different arrangements of epithelial cells layers?
Simple
Pseudostratified
Stratified
What are simple epithelium layers, and what are they for?
These are a single layer of cells
They are for diffusion & osmosis, filtration, secretion, and absorption
What are pseudostratified epithelium, and what are they for?
These appear to have multiple layers because the cell nuclei lie at different levels, and not all cells reach the apical surface. These are actually a type of simple epithelium since all of the cells rest on the basement membrane.
Cells that reach the apical surface may contain cilia and others can secrete mucous
Which pseudostratified epithelium secretes mucous?
Goblet cells
What are stratified epithelium, and what is it for?
This is a type of epithelium that is made up of two or more layers of cells.
It protects underlying tissues in locations with wear and tear
What are the 4 cell shapes of epithelia?
Squamous cells
Cuboidal cells
Columnar cells
Transitional cells
What are squamous cells and what are they for?
These are thin epithelial cells and allow for rapid passage of substances through them
What are cuboidal cells and what are they for?
These are equivalently tall and wide epithelial cells shaped like cubes or hexagons. They may have microvilli at their apical surface and function in either secretion or absorption
What are columnar cells and what are they for?
These are tall epithelial cells like columns that protect underlying tissues. Their apical surfaces may have cilia or microvilli, and usually specialize in secretion and absorption
What are transitional cells and what are they for?
These change shape from flat to cuboidal and back in organs that stretch to a larger size and then collapse to a smaller size like in the urinary bladder
Describe the appearance of simple squamous epithelium
Single layer of flat cells resembling a tiled floor when looking from the apical view
Centrally located oval- or spherically-shaped flattened nucleus
Where are simple squamous epithelia located?
Lines:
Heart
Blood vessels
Lymphatic vessels
Air sacs of lungs
Glomerular (Bowman’s) capsule of kidneys
Inner surface of the tympanic membrane Peritoneum
Describe the function of simple squamous epithelium
Filtration
Diffusion
Osmosis
Secretion in serous membranes
Endothelium is an example of what type of tissue, and where is it located?
This is a type of simple squamous epithelium that lines the heart, blood vessels, and lymphatic vessels
Mesothelium is an example of what type of tissue, and where is it located?
This is a type of simple squamous epithelium that lines serous membranes like the peritoneum, pleura, or pericardium
Describe the appearance of simple cuboidal epithelium
Single layer of cube-shaped cells. Easily recognized from the side view
Round, centrally located nucleus.
Where are simple cuboidal epithelia located?
Lines kidney tubules and smaller ducts of many glands
Makes up the secreting portion of the thyroid gland
Covers surface of ovary
Lines anterior surface of the eye lens capsule, and forms the pigmented epithelium at the posterior surface of the eye.
Describe the function of simple cuboidal epithelium
Secretion and absorption
Describe the appearance of non-ciliated simple columnar epithelium
Single layer of non-ciliated columnar cells with nuclei near bases of cells
Includes cells with microvilli and goblet cells.
Describe microvilli
They are microscopic fingerlike projections which increase the surface area of the plasma membrane, increasing the rate of absorption by the cell
Describe goblet cells
They are modified columnar cells that secrete mucus at their apical surfaces. Before release, mucus accumulates in upper portion of cell, causing it to bulge and making the whole cell resemble a goblet or wine glass.
Where are non-ciliated simple columnar epithelia located?
They line most of the GIT (from stomach to anus), ducts of many glands, and gallbladder
Describe the function of non-ciliated simple columnar epithelia
These are for secretion and absorption. Secretion of mucous lines the digestive, respiratory, and reproductive tracts completely, and most of the urinary tract.
The appearance of ciliated simple columnar epithelia
Single layer of ciliated column‐like cells with nuclei near bases
Includes goblet cells in some locations.
Where are ciliated simple columnar epithelia located?
Lines some portions of the upper respiratory tract, uterine (fallopian) tubes, uterus, some paranasal sinuses, and central canal of spinal cord
Describe the function of ciliated simple columnar epithelia
Mucus secreted by goblet cells forms a film over respiratory surface that traps inhaled foreign particles.
Cilia wave in unison to move mucus and foreign particles toward throat to be coughed up and swallowed/spit out Cilia also help move oocytes expelled by the ovaries through uterine tubes into uterus
Describe the appearance of non-ciliated pseudostratified columnar epithelia
Looks like several layers because the nuclei of the cells are at various levels.
All cells are attached to the basement membrane in a single layer but some cells do not extend to the apical surface. When viewed from the side, these features give the false impression of a multilayered tissue.
Includes cells without cilia and also lacks goblet cells.
Where are non-ciliated pseudostratified columnar epithelia found?
Lines epididymis, larger ducts of many glands like the parotid, and parts of male urethra.
What are non-ciliated pseudostratified columnar epithelia for?
Absorption and secretion
Describe the appearance of ciliated pseudostratified columnar epithelia
Looks like several layers because the nuclei of the cells are at various levels.
All the cells are attached to the basement membrane in a single layer but some do not extend to the apical surface. When viewed from the side, these features give the false impression of a multilayered tissue
Contains cells that extend to the surface and either contain cilia or secrete mucus (goblet cells).
Where are ciliated pseudostratified columnar epithelia located?
Lining of most of the upper respiratory tract
What are stratified columnar epithelia for
Secretes mucus that traps foreign particles, and the cilia sweep away the mucus for eventual elimination from the body.
Describe the appearance of stratified squamous epithelia
Two or more layers of cells
Upper cells are squamous while those in the deep layers vary in shape from cuboidal to columnar.
Basal cells continually undergo cell division. As new cells grow, cells of basal layer are pushed upward toward surface and become dehydrated, shrunken, and harder because they are farther from the blood supply in the underlying connective tissue.
At apical layer, cells lose their cell junctions and are sloughed off, but are replaced as new cells continually emerge from basal cells
What are the two types of stratified squamous epithelium
Keratinized and non-keratinized
What is keratinized stratified squamous epithelium?
This is stratified squamous epithelium that has a tough layer of keratin in apical layer and several layers deep to it to help protect the skin and underlying tissues from microbes, heat, and chemicals
What is non-keratinized stratified squamous epithelium?
Nonkeratinized stratified squamous epithelium does not contain keratin in the apical layer or several layers deep and remains moist.
Where is keratinized stratified squamous epithelium found?
Superficial layers of the skin
Where is non-keratinized stratified squamous epithelium found?
Lines wet surfaces such as the mouth, esophagus, part of the epiglottis, part of the pharynx, vagina, and the tongue
What is the function of stratified squamous epithelia?
Protection - it is the first line of defense against microbes
Describe the appearance of stratified cuboidal epithelia
Two or more layers of cells, with the apical layer being cube‐shaped; fairly rare type.
Where are stratified cuboidal epithelia located?
They are located in the ducts of adult sweat glands and esophageal glands, and part of male urethra.
What are stratified cuboidal epithelia for?
These provide protection and limited secretion and absorption
Describe the appearance of stratified columnar epithelia
The basal layers usually consists of shortened, irregularly shaped cells; only apical layer has columnar cells; uncommon
Where are stratified columnar epithelia located?
Lines part of urethra, large excretory ducts of some glands like the esophageal glands, small areas in anal mucous membrane, and part of conjunctiva of eye.
What are stratified columnar epithelia for?
These provide protection and secretion
Describe the appearance of transitional epithelia (urothelium)
Appearance is variable (transitional). In its relaxed or unstretched state, transitional epithelium looks like stratified cuboidal epithelium, except that the cells in the apical layer tend to be large and rounded. As the tissue is stretched, its cells become flatter, giving the appearance of stratified squamous epithelium
Where is transitional epithelia located?
Because of its multiple layers and elasticity, it is ideal for lining hollow structures (such as the urinary bladder) that are subject to expansion from within.
It also lines portions of the ureters and urethra
What are the two types of glands in the body?
Endocrine and exocrine
How do secretions of the endocrine glands travel?
These enter interstitial fluid and then diffuse into the bloodstream without flowing through a duct
Give examples of endocrine glands
Pituitary gland at base of brain
Pineal gland in brain
Thyroid and parathyroid glands near larynx
Adrenal glands superior to kidneys
Pancreas near stomach
Ovaries in pelvic cavity
Testes in scrotum
Thymus in thoracic cavity.
How do secretions of exocrine glands travel?
Secretions move into ducts that empty at surface epithelium like the skin or the lumen of an organ.
Give examples of exocrine secretions
Mucus
Perspiration
Oil
Earwax
Milk
Saliva
Digestive Enzymes
Give examples of exocrine glands
Sweat glands
Salivary glands
Pancreas
What are the two basic elements of connective tissue?
Cells and extracellular matrix
What does the extracellular matrix consist of?
Protein fibers and ground substance
What are the general features of connective tissues?
Do not usually occur on body surfaces
Highly vascular except for the cartilage and tendons
Supplied with nerves except for cartilage
What are flibroblasts?
These are large, flat cells with branching processes. They are present in several connective tissues, and are usually the most numerous
What are macrophages?
These are phagocytes that develop from monocytes, a type of white blood cell
What are plasma cells?
These are the most important part of the body’s immune response
What are mast cells?
These are involved in the inflammatory response and kill bacteria
What are adipocytes?
These are fat cells
What does the extracellular matrix consist of?
A fluid, gel, or solid ground substance plus protein fibers
What is ground substance?
This is the component of connective tissue between cells and fibers.
What does ground substance do?
Supports cells
Binds cells together
Provides medium through which substances are exchanged between blood and cells
What is hyaluronic acid?
This is a viscous polysaccharide that binds cells together, lubricates joints, and helps to maintain the shape of the eyes.
How is ground substance involved in phagocyte migration through connective tissue?
White blood and sperm cells, and some bacteria produce hyaluronidase which causes hyaluronic acid to break down and become watery. By breaking down the hyaluronic acid, WBC can move through connective tissues to reach sites of infection, and sperm cells can penetrate the ovum during fertilization.
This is also how some bacteria is able to spread through connective tissues.
What is chondroitin sulfate?
This is polysaccharide ground substance that provides support and adhesiveness in connective tissues in bone, cartilage, skin, and blood vessels.
What are the 3 types of fibers embedded in the extracellular matrix between cells?
Collagen
Elastic
Reticular
What are collagen fibers?
These are strong fibers that resist pulling forces, but they are not stiff and instead promote tissue flexibility.
They often occur in bundles lying parallel to one another, allowing for great strength
Where are collagen fibers found?
Most connective tissues, especially bone, cartilage, tendons, and ligaments
What are elastic fibers?
These are smaller in diameter than collagen fibers and branch together to make a network within a tissue. It is made up of a protein called elastin, and is surrounded by a glycoprotein called fibrillin, which is key for the stability of the fiber.
They are strong, and can be stretched up to 1.5x their relaxed length without breaking. They are able to return to their original shape after being stretched.
Where are elastic fibers found?
Plentiful in skin, blood vessel walls, and lung tissue
What are reticular fibers?
These are fibers made of collagen and a coating of glycoprotein, which provides support in many soft organs, including the walls of blood vessels. They also form branching networks around fat cells, nerve fibers, and skeletal and smooth muscle cells.
These fibers also help to make the basement membrane
What are the 3 main types of connective tissue?
Loose connective tissue
Dense connective tissue
Supporting connective tissue
What are the 3 types of loose connective tissue?
Areolar connective tissue
Adipose tissue
Reticular connective tissue
What are the 3 types of dense connective tissue?
Dense regular connective tissue
Dense irregular connective tissue
Elastic connective tissue
What are the 3 types of supporting connective tissue?
Cartilage
Bone tissue
Liquid connective tissue
What are the 3 types of cartilage?
Hyaline cartilage
Fibrocartilage
Elastic cartilage
What are the 2 types of liquid connective tissue
Blood
Lymph
What forms the subcutaneous layer?
This is made of adipose tissue and areolar connective tissue
Where are areolar connective tissue found?
These are found in almost every body structure
Subcutaneous layer deep to skin
Superficial region of dermis of skin
Connective tissue layer of mucous membranes
Around blood vessels, nerves, and body organs
What are areolar connective tissues for?
These are for strength, elasticity, and support
What is adipose tissue?
This is tissue made up of adipocytes that are specialized for the storage of triglycerides
Describe the structure of adipocytes
They fill up with a single large droplet of triglyceride, causing the cytoplasm and nucleus to be pushed to the periphery of the cell.
Where is adipose tissue located?
It is located wherever areolar connective tissue is located
Subcutaneous layer deep to the skin
Around the heart and kidneys
Yellow bone marrow
Padding around joints and behind the eyeball in the eye socket
What is adipose tissue for?
It reduces heat loss through skin
Acts as an energy reserve
Supports and protects organs
What is reticular connective tissue?
This is the fine interlacing network of reticular fibers and reticular cells
What are reticular fibers?
These are a thin form of collagen fiber
Where is reticular tissue located?
It is the supporting framework (or stroma) of the liver, spleen, and lymph nodes
Red bone marrow
part of the basement membrane
Around blood vessels and muscles
What is reticular connective tissue for?
Forms stroma of organs
Binds smooth muscle tissue cells together
Filters and removes worn out blood cells in the spleen and microbes in lymph nodes
What is dense regular connective tissue?
This consists mainly of collagen fibers regularly arranged in bundles.
Fibroblasts are present in rows between the bundles.
Its extracellular matrix looks shiny white
Why do damaged tendons and ligaments heal slowly?
This is because collagen fibers are not living cells, but instead protein structures that are secreted by fibroblasts
Where is dense regular connective tissue found?
This forms tendons (muscle to bone attachments), most ligaments (bone to bone attachments), and aponeuroses (sheetlike tendons making muscle to muscle or muscle to bone attachments)
What is dense regular connective tissue for?
This is makes strong attachments between different structures. The tissue structures resist pulling along the long axis of the fibers.
What is dense irregular connective tissue?
This is mostly made of collagen fibers randomly arranged and a few fibroblasts
Where is dense irregular connective tissue found?
They often occur in sheets like fasciae
Deeper regions of dermis of the skin
Periosteum of bone
Perichondrium of cartilage
Joint capsules
Membrane capsules around various organs
Pericardium of the heart
Heart valves
What is dense irregular connective tissue for?
It provides tensile (pulling) strength in many directions
What is elastic connective tissue?
This is mostly made of elastic fibers
Fibroblasts are present in spaces between fibers
Unstained tissues are yellowish
Where is elastic connective tissue located?
Lung tissue
Walls of elastic arteries
Trachea
Bronchial tubes
True vocal cords
Suspensory ligaments of the penis
Some ligaments between vertebrae
What is elastic connective tissue for?
This is allows for the stretching of various organs.
It is strong and can recoil to its original shape after being stretched
Elasticity is important to normal functioning of lung tissue and elastic arteries
What is responsible for the resilience of cartilage?
Chondroitin sulfate
What is are chondrocytes?
These are the cells of mature cartilage. It occurs singly or in groups within spaces called lacunae
Why does cartilage not have a blood supply?
Because it secretes an anti-angiogenesis factor to prevent blood vessel growth.
Why does cartilage heal poorly after injury?
It has no blood supply
What is hyaline cartilage?
This is the most abundant type of cartilage in the body. It contains a resilient gel as ground substance and looks like a shiny bluish-white substance.
It is the weakest type of cartilage.
Where is hyaline cartilage found?
Ends of long bones
Anterior ends of ribs
Nose
Part of larynx
Trachea
Bronchi
Bronchial tubes
Embryonic and fetal skeleton
What is hyaline cartilage for?
Provides smooth surfaces for movements at joints
Flexibility and support
What is fibrocartilage?
This is made up of chondrocytes scattered among thick bundles of collagen fibers in the extracellular matrix
Where is fibrocartilage located?
The pubic symphysis - point where hip bones join anteriorly
Intervertebral disks
Menisci (cartilage pads) of the knee
Portions of tendons that insert into cartilage
What is the function of fibrocartilage?
Supporting and joining structures together
Strength and rigidity make it the strongest type of cartilage
What is elastic cartilage?
This is made up of chondrocytes found in a threadlike network of elastic fibers in the extracellular matrix. It has a perichondrium present
Where is elastic cartilage found?
It is at the top of the larynx (epiglottis)
External part of the ear (auricle)
Auditory (Eustachian) tubes
What is elastic cartilage for?
This provides strength and elasticity
Maintains the shape of certain structures
What are the functions of bone tissue?
It supports soft tissues
Protects delicate structures
Works with skeletal muscles to generate movement
What is blood tissue?
Aka blood, it is connective tissue with a liquid extracellular matrix called blood plasma
What is blood plasma?
This is a pale yellow fluid that is made up of mostly water, with many dissolved substances such as nutrients, wastes, enzymes, hormones, respiratory gases, and ions. It suspends red blood cells, white blood cells, and platelets
What are red blood cells for?
These transport oxygen to body cells and remove carbon dioxide from them
What are white blood cells for?
These are involved in phagocytosis, immunity, and allergic reactions
What are platelets for?
Blood clotting
What is lymph?
This is the fluid that flows in lymphatic vessels. It is a connective tissue that is made up of several types of cells.
Its extracellular matrix is similar to blood plasma, but with much less protein.
