LESSON 4: TISSUES Flashcards
group of cells with similar structure and function
tissues
study of tissues
histology
A physician who examine cells and tissue
pathologist
a physician who examines cells and tissues to help other physicians make accurate diagnoses.
pathologist
One of the principal functions of a pathologist is to
examine tissues for any changes that might indicate disease
types of tissues
epithelial
connective
muscular
nervous
Cell Junctions
tight junctions
adherens junctions
desmosome
hemidesmosome
gap junction
consist of weblike strands of transmembrane proteins that fuse together the outer surfaces of adjacent plasma membranes to seal off passageways between adjacent cells
They inhibit the passage of substances between cells and prevent the contents of these organs from leaking into the blood or surrounding tissues.
tight junctions
bind adjacent cells together
ex. intestines
tight junctions
mechanical links that bind cells
Desmosomes: (cadherins)
Help epithelial surfaces resist separation during contractile activities
Adherens: (cadherins)
bind cells to the basement membrane
Hemidesmosomes: (integrins)
- small channels that allow molecules to pass between cells
- allow cells to communicate
- most common
Gap junctions: (connexins)
- covers body surfaces and lines hollow organs, body cavities, and ducts; it also forms glands.
- allows the body to interact with both its internal and external environments.
epithelial tissue
- Cover and line body surfaces
- Often form sheets with one free surface, the apical surface, and an anchored surface, the basement membrane
- Avascular (no blood supply)
- Regenerate easily if well nourished
Hallmarks of epithelial tissues:
Classification of Epithelium Based on Cell Layers (Arrangement of Layers)
Simple epithelium
stratified epithelium
pseudostratified epithelium
- Consists of only a single layer of cells; Secretion, absorption
Simple Epithelium
consists of more than one layer of epithelial cells, with some cells sitting on top of others.
Stratified Epithelium
Appeared to be 2 or more layers of cells, some are tall and others are short
Pseudostratified Epithelium
Classification of Epithelium Based on Idealized Shapes (Cell shapes)
Squamous
Cuboidal
Columnar
flat or scalelike; rapid passage of substances
squamous cells
cube-shaped; may have microvilli; secretion and absorption
cuboidal cells
tall and thin, cell tends to be taller than they are wide; secretion and absorption; protect underlying tissues
columnar cells
change shape, from squamous to cuboidal and back, as organs such as the urinary bladder stretch (distend) to a larger size and then collapse to a smaller size
transitional cells
Major Types of Epithelial Tissues
- Simple squamous epithelium
- Simple cuboidal epithelium
- Simple columnar epithelium
- Pseudostratified epithelium
- Stratified squamous epithelium
- Stratified cuboidal epithelium
- Stratified columnar epithelium
- Transitional epithelium
- single layer of flat cells that resembles a tiled floor when viewed from apical surface; centrally located nucleus that is flattened and oval or spherical in shape
simple squamous epithelium
- lines the cardiovascular and lymphatic system (heart, blood vessels, lymphatic vessels), where it is known as _________ and forms the epithelial layer of serous membranes where it is called ________
endothelium
mesothelium
simple squamous epithelium
FUNCTION:
- presents at sites of filtration (such as blood filtration in kidneys) or diffusion (such as diffusion of oxygen into blood vessels of lungs) and at site of secretion in serous membrane
- not found in body areas subject to mechanical stress (wear and tear)
simple squamous epithelium
- single layer of cube-shaped cells; some cells have microvilli (kidney tubules) or cilia (terminal bronchioles of the lungs)
- secretion and absorption by cells of the kidney tubules; secretion by cells of glands and choroid plexuses; movement of particles embedded in mucus out of the terminal bronchioles by ciliated cells
location: kidney tubules, glands and their ducts, choroid plexuses of the brain, lining of terminal bronchioles of the lungs, and surfaces of the ovaries
simple cuboidal epithelium
single layer of tall, narrow cells; some cells have cilia (bronchioles of lungs, auditory tubes, uterine tubes, and uterus) or microvilli (intestines)
simple columnar epithelium
movement of particles out of the bronchioles of the lungs by ciliated cells; partially responsible for the movement of oocytes through the uterine tubes by ciliated cells; secretion by cells of the glands, the stomach, and the intestine; absorption by cells of the intestine
location: glands and some ducts, bronchioles of lungs, auditory tubes, uterus, uterine tubes, stomach, intestines, gallbladder, bile ducts, and ventricles of the brain
simple columnar epithelium
single layer of cells; some cells are tall and thin and reach the free surface, and others do not; the nuclei of these cells are at different levels and appear stratified; the cells are almost always ciliated and are associated with goblet cells that secrete mucus onto the free surface
pseudostratified columnar epithelium
synthesize and secrete mucus onto the free surface and move mucus (of fluid) that contains foreign particles over the surface of the free surface and from passages
location: lining of nasal cavity, nasal sinuses, auditory tubes, pharynx, trachea, and bronchi of lungs
pseudostratified columnar epithelium
- several layers of cells that are cuboidal in the basal layer and progressively flattened toward the surface; the epithelium can be nonkeratinized (moist) or keratinized;
- surface cells retain a nucleus and cytoplasm (nonkeratinized stratified epithelium)
- cytoplasm of cells at the surface is replaced by a protein called keratin, and the cells are dead (keratinized stratified epithelium)
stratified squamous epithelium
protects against abrasion, forms a barrier against infection, and reduces loss of water from the body
location:
keratinized - outer layer of the skin;
nonkeratinized - mouth, throat, larynx, esophagus, anus, vagina, inferior urethra, and corneas
stratified squamous epithelium
- consists of more than one layer of cuboidal epithelial cells.
stratified cuboidal epithelium
- This epithelial type is relatively rare and is found in sweat gland ducts, ovarian follicular cells, and the salivary glands.
stratified cuboidal epithelium
- It functions in absorption, secretion, and protection.
stratified cuboidal epithelium
- consists of more than one layer of epithelial cells, but only the surface cells are columnar
stratified columnar epithelium
- stratified cells that appear cuboidal when the organ or tube is not stretched and squamous when the organ or tube is stretched by fluid
- accommodates fluctuations in the volume of fluid in an organ or a tube; protects against the caustic effects of urine
- location: lining of urinary bladder, ureters, and superior urethra
transitional epithelium
Two major gland types develop from epithelial sheets
endocrine glands and exocrine glands
Ductless; secretions (hormones) diffuse into blood vessels
Examples: thyroid, adrenals, and pituitary
endocrine glands
Secretions empty through ducts to the epithelial surface
Include sweat and oil glands, liver, and pancreas (both internal and external)
exocrine glands
It is usually characterized by large amounts of extracellular material that separates cells from one another
connective tissue
functions of connective tissue
protection
support
binding
characteristics of connective tissue
variations in blood supply
extracellular matrix
Some tissue types are well vascularized
Some have a poor blood supply or are avascular
variations in blood supply
Nonliving material that surrounds living cells
extracellular matrix
types of protein fibers
collagen fibers
reticular fibers
elastic fibers
resemble microscopic ropes, are flexible but resist stretching
collagen fibers
very fine, short collagen fibers that branch to form a supporting network
reticular fibers
have a structure similar to that of coiled metal bed springs; after being stretched, they can recoil to their original shape
elastic fibers
Adult connective tissue consists of three types:
connective tissue proper (loose and dense)
supporting connective tissue (cartilage and bone)
fluid connective tissue (blood)
consists of relatively few protein fibers that form a lacy network, with numerous spaces filled with ground substance and fluid
Loose connective tissue
Three subdivisions of loose connective tissue are
areolar
adipose
reticular
- fine network of fibers (mostly collagen fibers with a few elastic fibers) with spaces between the fibers; fibroblasts, macrophages, and lymphocytes are located in the spaces
- loose packing, support, and nourishment for the structures with which it is associated
- widely distributed throughout the body; substance on which epithelial basement membranes rest; packing between glands, muscles, and nerves; attaches the skin to underlying tissues
areolar connective tissue
- little extracellular matrix surrounding cells; the adipocytes, or fat cells, are so full of lipid that the cytoplasm is pushed to the periphery of the cell
- packing material, thermal insulator, energy storage, and protection of organs against injury from being bumped or jarred
- predominantly in subcutaneous areas, mesenteries, renal pelves, around kidneys, attached to the surface of the colon, mammary glands, and in loose connective tissue that penetrates into spaces and crevices
adipose tissue
- fine network of reticular fibers irregularly arranged
- provides a superstructure for lymphatic and hemopoietic tissues
- within the lymph nodes, spleen, bone marrow
reticular tissue
has a relatively large number of protein fibers that form thick bundles and fill nearly all of the extracellular space.
dense connective tissue
two major subcategories of dense connective tissue:
collagenous and elastic
- matrix composed of collagen fibers running in somewhat the same direction in tendons and ligaments; collagen fibers run in several directions in the dermis of the skin and in organ capsules
- withstand great pulling forces exerted in the direction of fiber orientation due to great tensile strength and stretch resistance
- tendons (attach muscle to bone) and ligaments (attach bones to each other); also found in the dermis of the skin, organ capsules, and the outer layer of many blood vessels
dense regular collagenous connective tissue
- matrix composed of collagen fibers and elastin fibers running in somewhat the same direction in elastic ligaments; elastic fibers run in connective tissue of blood vessel walls
- capable of stretching and recoiling like a rubber band with strength in the direction of fiber orientation
- elastic ligaments between the vertebrae and along the dorsal aspect of the neck (nucha) and in the vocal chords; also found in elastic connective tissue of blood vessel walls
dense regular elastic connective tissue
provides support, but if bent or slightly compressed, it resumes its original shape.
cartilage
three types of cartilage:
- hyaline
- fibrocartilage
- elastic cartilage
- collagen fibers are small and evenly dispersed in the matrix, making the matrix appear transparent; the chondrocytes are found in spaces, or lacunae, within the firm but flexible matrix
- allows growth of long bones; provides rigidity with some flexibility in the trachea, bronchi, ribs, nose; forms strong, smooth, yet somewhat flexible articulating surfaces; forms the embryonic skeleton
- growing long bones, cartilage rings of the respiratory system, costal cartilage of ribs, nasal cartilages, articulating surface of bones, and the embryonic skeleton
hyaline cartilage
- collagen fibers similar to those in hyaline cartilage; the fibers are numerous than in other cartilages and are arranged in thick bundles
- somewhat flexible and capable of withstanding considerable pressure; connects structures subjected to great pressure
- intervertebral disks, pubic symphysis, and articular disks (knees and temporomandibular [jaw] joints)
fibrocartilage
- similar to hyaline cartilage, but matrix also contains elastin fibers
- provides rigidity with even more flexibility than hyaline cartilage because elastic fibers return to their original shape after being stretched
- external ears, epiglottis, and auditory tubes
elastic cartilage
- hard bony matrix predominates; many osteocytes are located within lacunae; matrix is organized into layers called lamellae
- provides great strength and support and protects internal organs (brain); also provides attachment sites for muscles and ligaments; the joints of bones allow movements
- all bones of the body
bone
Contains large spaces and in which the extracellular matrix is arranged as little beams called trabeculae.
spongy bone
- blood cells and a fluid matrix
- transports oxygen, CO2, hormones, nutrients, wastes, etc; protects the body from infections and is involved in temperature regulation
- within the blood vessels; white blood cells frequently leave the blood vessels and enter the interstitial spaces
blood
- participate in blood clotting mechanism
platelets or thromobocytes
specialized for contraction having properties of extensibility, elasticity and contractility. It is highly vascularized and innervated
muscular tissue
- Packaged by connective tissue sheets into skeletal muscles, which are attached to the skeleton and pull on bones or skin
- Voluntarily (consciously) controlled
- Produces gross body movements or facial expressions
skeletal muscle tissue
Characteristics of skeletal muscle cells
striations (stripes)
multinucleate (more than one nucleus)
long, cylindrical shape
3 types of muscle tissue and cell
smooth muscle, cardiac muscle, skeletal muscle
- appear striated (bonded); cells are large, long, and cylindrical, with many nuclei
- movement of the body; under voluntary control
- attached to bone or other connective tissue
skeletal muscle
- cylindrical and striated and have a single nucleus; they are branched and connected to one another by intercalated disks, which contain gap junctions
- pumps the blood; under involuntary (unconscious) control
- in the heart
cardiac muscle
- tapered at each end, are not striated, and have a single nucleus
- regulates the size of organs, forces fluid through tubes, controls the amount of light entering the eye, and produces “goose bumps” in the skin; under involuntary (unconscious) control
- in hollow organs, such as the stomach and intestine; skin and eyes
smooth muscle
Consists of two types of principal cells – neurons and neuroglia.
nervous tissue
- Function is to receive and conduct electrochemical impulses to and from body parts
- Composed of neurons and nerve support cells
nervous tissue
Irritability
Conductivity
Support cells called ______ insulate, protect, and support neurons
neuroglia
- a neuron consists of dendrites, a cell body, and a long axon; neuroglia, or support cells, surround the neurons
- neurons transmit information in the form of action potentials, store information, and integrate and evaluate data; neuroglia support, protect, and form specialized sheaths around axons
- in the brain, spinal cord, and ganglia
nervous tissue
peripheral nervous system
satellite cells
schwann cells
central nervous system
microglia
ependymal cells
oligodendrocytes
astrocytes
