What factors influence the structure and properties of a specific tissue?
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The nature of the extracellular material that surrounds the tissue cells and the connections between the cells that compose the tissue.
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What factors influence the structure and properties of a specific tissue?
The nature of the extracellular material that surrounds the tissue cells and the connections between the cells that compose the tissue.
What is a tissue in the context of the human body?
A tissue is a group of cells that work together to perform specific functions in the body.
What are the main functions of ciliated pseudostratified columnar epithelium?
secrete mucus that traps foreign particles and to use cilia to sweep away mucus for elimination from the body.
What is the appearance of ciliated pseudostratified columnar epithelium and why?
Appears to have several layers because cell nuclei 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, giving a false impression of a multilayered tissue.
What is the main structural difference between epithelial tissue and connective tissue?
Epithelial tissue has many cells tightly packed together with little to no extracellular matrix, while connective tissue has a few scattered cells surrounded by large amounts of extracellular matrix.
Where are tight junctions commonly found?
Stomach, intestines, and urinary bladder.
What are the functions of simple squamous epithelium?
sites of filtration (such as blood filtration in kidneys)
or diffusion (such as diffusion of oxygen into blood vessels of lungs)
sites of secretion in serous membranes.
It is not found in body areas subject to mechanical stress (wear and tear).
What is the structure of tight junctions?
Tight junctions consist of weblike strands of transmembrane proteins that fuse together the outer surfaces of adjacent plasma membranes to seal off passageways between adjacent cells.
What is the function of transitional epithelium in urinary organs?
Transitional epithelium allows urinary organs to stretch and maintain a protective lining while holding variable amounts of fluid without rupturing.
What is the function of ciliated simple columnar epithelium?
Cilia beat in unison, moving mucus and foreign particles toward the throat, where they can be coughed up and swallowed or spit out. Cilia also help move oocytes expelled from ovaries through uterine tubes into the uterus.
What is histology?
Histology is the science that deals with the study of tissues.
Where is ciliated pseudostratified columnar epithelium commonly located?
It lines the airways of most of the upper respiratory tract.
What type of cell junction prevents the contents of organs from leaking into surrounding tissues?
Tight junctions.
What relationship between epithelial tissue and connective tissue is important for the survival and function of epithelial tissues?
The relationship where epithelial tissue relies on the connective tissue for support and nutrient exchange.
Where can stratified columnar epithelium be found?
It lines part of the urethra, large excretory ducts of some glands (such as esophageal glands), small areas in the anal mucous membrane, and part of the conjunctiva of the eye.
What are adherens junctions and what is their function?
Adherens junctions contain plaque and cadherins that join cells. They help epithelial surfaces resist separation during contractile activities.
What is the function of hemidesmosomes?
Hemidesmosomes anchor cells to the basement membrane using integrins.
Describe the structure of stratified columnar epithelium.
Basal layers usually consist of shortened, irregularly shaped cells; only the apical layer has columnar cells.
What are the four basic types of tissues in the human body?
The four basic types of tissues are epithelial, connective, muscular, and nervous tissues.
What are the characteristics of stratified squamous epithelium?
Stratified squamous epithelium has two or more layers of cells; cells in the apical layer and several layers deep to it are squamous, while cells in deeper layers vary from cuboidal to columnar. As basal cells divide, daughter cells push upward toward the apical layer, becoming dehydrated and less metabolically active as they move away from the blood supply.
Where is stratified cuboidal epithelium commonly found?
It is found in the ducts of adult sweat glands and esophageal glands, and part of the male urethra.
How do endocrine gland secretions reach the bloodstream?
Endocrine gland secretions enter the interstitial fluid and then diffuse into the bloodstream without flowing through a duct.
What are the two criteria used to categorize multicellular exocrine glands?
Multicellular exocrine glands are categorized according to whether their ducts are branched or unbranched and the shape of the secretory portions of the gland.
What is the description of simple squamous epithelium?
Simple squamous epithelium is a single layer of flat cells that resembles a tiled floor when viewed from the apical surface; it has a centrally located nucleus that is flattened and oval or spherical in shape.
Where is keratinized stratified squamous epithelium typically found?
Keratinized stratified squamous epithelium forms the superficial layer of the skin.
What are the main functions of simple cuboidal epithelium?
Secretion and absorption.
What are the two main types of epithelial tissue?
The two main types of epithelial tissue are covering and lining epithelium (surface epithelium) and glandular epithelium.
How often should Pap tests be performed for females aged 30 to 65?
Females aged 30 to 65 should have Pap testing and HPV testing (cotesting) every five years or a Pap test alone every three years.
What are some examples of the consistency of tissues?
Tissues may be hard (bone), semisolid (fat), or liquid (blood).
What is the difference between keratinized and nonkeratinized stratified squamous epithelium?
Keratinized stratified squamous epithelium develops a tough layer of keratin in the apical layer of cells and several layers deep to it, while nonkeratinized stratified squamous epithelium does not contain large amounts of keratin and is constantly moistened by mucus.
What are the functions of stratified cuboidal epithelium?
Protection; limited secretion and absorption.
What are the functions of connective tissue?
Connective tissue protects and supports the body and its organs, binds organs together, stores energy reserves as fat, and provides immunity to disease-causing organisms.
What are the functions of epithelial tissue?
Epithelial tissue functions to protect, secrete (mucus, hormones, and enzymes), absorb (nutrients in the gastrointestinal tract), and excrete (various substances in the urinary tract).
Where do exocrine glands secrete their products?
Exocrine glands secrete their products into ducts that empty onto the surface of a covering and lining epithelium such as the skin surface or the lumen of a hollow organ.
What is the role of hemidesmosomes in epithelial cells?
Hemidesmosomes in the basal surfaces of the deepest layer of epithelial cells anchor the epithelium to the basement membrane.
Describe a simple branched tubular gland.
A gland where the tubular secretory part is branched and attaches to a single unbranched duct. Example: gastric glands.
What role do gap junctions play in cell communication?
Gap junctions allow ions and small molecules to diffuse between neighboring cells, facilitating communication and the spread of nerve or muscle impulses.
Where is nonkeratinized stratified squamous epithelium typically found?
Nonkeratinized stratified squamous epithelium lines wet surfaces such as the lining of the mouth, esophagus, part of the epiglottis, part of the pharynx, and vagina, and covers the tongue.
How are glands of the body classified?
All glands of the body are classified as either endocrine or exocrine.
What is the characteristic of pseudostratified epithelium?
Pseudostratified epithelium appears to have multiple layers of cells because the cell nuclei lie at different levels, but it is actually a simple epithelium because all its cells rest on the basement membrane.
What are examples of multicellular exocrine glands?
Examples of multicellular exocrine glands include sudoriferous (sweat), sebaceous (oil), and salivary glands.
What is the functional classification of exocrine glands based on?
It is based on how their secretions are released.
What are the five most important types of cell junctions?
The five most important types of cell junctions are tight junctions, adherens junctions, desmosomes, hemidesmosomes, and gap junctions.
Where is transitional epithelium located in the body?
Transitional epithelium lines the urinary bladder and portions of the ureters and urethra.
How do desmosomes differ from adherens junctions?
Desmosomes attach to intermediate filaments of the cytoskeleton, while adherens junctions attach to microfilaments.
What is the description of ciliated simple columnar epithelium?
Ciliated simple columnar epithelium is a single layer of ciliated columnlike cells with oval nuclei near the base of cells. Goblet cells are usually interspersed.
What is the description of nonciliated pseudostratified columnar epithelium?
Nonciliated pseudostratified columnar epithelium appears to have several layers because the nuclei of the cells are at various levels. Even though all the cells are attached to the basement membrane in a single layer, some cells do not extend to the apical surface. It contains cells without cilia and lacks goblet cells.
Why are epithelial and connective tissues found adjacent to each other?
Epithelial tissue lacks blood vessels and forms surfaces, so it is always found adjacent to blood vessel-rich connective tissue to enable exchanges with blood necessary for oxygen and nutrient delivery and waste removal.
What is the function of the basement membrane?
The basement membrane attaches epithelial cells to underlying connective tissue, providing structural support and regulating exchanges between the epithelium and connective tissue.
What are the characteristics of squamous cells?
Squamous cells are thin and flat, which allows for the rapid passage of substances through them.
Describe a simple acinar gland.
A gland where the secretory portion is rounded and attaches to a single unbranched duct. Example: glands of penile urethra.
To what class of glands do sebaceous (oil) glands belong?
Holocrine glands.
What are cell junctions?
Cell junctions are contact points between the plasma membranes of tissue cells.
What types of cells are found in ciliated pseudostratified columnar epithelium?
It contains cells that extend to the surface and secrete mucus (goblet cells) or bear cilia.
What makes transitional epithelium ideal for lining hollow structures like the urinary bladder?
Its multiple layers and elasticity make it ideal for lining hollow structures subject to expansion from within.
What are exocrine glands and where do they release their secretory products?
Exocrine glands release their secretory products into ducts that empty onto the surface of a covering and lining epithelium, such as the skin surface or the lumen of a hollow organ.
Where is ciliated simple columnar epithelium located?
It lines some bronchioles of the respiratory tract, uterine tubes, uterus, some paranasal sinuses, central canal of the spinal cord, and ventricles of the brain.
What are the functions of stratified columnar epithelium?
Protection and secretion.
What are the characteristics of epithelial tissue?
Epithelial tissue covers body surfaces and lines hollow organs, body cavities, and ducts; it also forms glands.
Where is nonciliated simple columnar epithelium located in the body?
It lines the gastrointestinal tract (from stomach to anus), ducts of many glands, and the gallbladder.
Why do endocrine secretions have far-reaching effects?
Endocrine secretions have far-reaching effects because they are distributed throughout the body by the bloodstream.
What proteins are found in the basal lamina of the basement membrane?
The basal lamina contains proteins such as laminin and collagen, as well as glycoproteins and proteoglycans.
What are transitional cells and where are they found?
Transitional cells change shape from squamous to cuboidal and back, as organs such as the urinary bladder stretch to a larger size and then collapse to a smaller size.
How do apocrine glands release their secretions?
The secretory product accumulates at the apical surface of the secreting cell, and that portion of the cell pinches off by exocytosis to release the secretion. Example: milk fats in the mammary glands.
Which type of cell junction functions in communication between adjacent cells?
Gap junctions function in communication between adjacent cells.
What is the appearance of transitional epithelium in a relaxed state?
In a relaxed state, transitional epithelium looks like stratified cuboidal epithelium, with apical layer cells that are large and rounded.
What substances do exocrine glands produce?
Exocrine glands produce substances such as sweat to help lower body temperature, oil, earwax, saliva, or digestive enzymes.
What is the role of a pathologist?
A pathologist is a physician who examines cells and tissues to help other physicians make accurate diagnoses.
What is the function of stratified epithelium?
Stratified epithelium consists of two or more layers of cells that protect underlying tissues in locations where there is considerable wear and tear.
What are the two characteristics used to classify covering and lining epithelial tissue?
Covering and lining epithelial tissue are classified according to the arrangement of cells into layers and the shapes of the cells.
How does transitional epithelium appear when stretched?
When stretched, transitional epithelium cells become flatter, giving the appearance of stratified squamous epithelium.
Where can exocrine glands be found in the body?
Exocrine glands can be found in the sweat, oil, and earwax glands of the skin, as well as in digestive glands such as salivary glands (secreting into the mouth cavity) and the pancreas (secreting into the small intestine).
What is the difference between simple and compound multicellular exocrine glands?
Simple multicellular exocrine glands have a single unbranched duct, while compound multicellular exocrine glands have a branched duct.
What is the function of nonciliated pseudostratified columnar epithelium?
Its functions are absorption and secretion.
What role do goblet cells play in nonciliated simple columnar epithelium?
Goblet cells are modified columnar epithelial cells that secrete mucus, a slightly sticky fluid, at their apical surfaces. The mucus accumulates in the upper portion of the cell, causing it to bulge and making the whole cell resemble a goblet or wine glass.
What are the general features of epithelial tissue?
Epithelial tissue consists of cells arranged in continuous sheets, in either single or multiple layers, with little intercellular space between adjacent plasma membranes.
What is the function of simple epithelium?
Simple epithelium functions in diffusion, osmosis, filtration, secretion, or absorption.
What is the function of glandular epithelium?
The function of glandular epithelium is secretion, which is accomplished by glandular cells that often lie in clusters deep to the covering and lining epithelium.
What is a compound gland?
A gland where the duct branches.
Describe a simple tubular gland.
A gland where the tubular secretory part is straight and attaches to a single unbranched duct. Example: glands in the large intestine.
Describe a compound tubular gland.
A gland where the secretory portion is tubular and attaches to a branched duct. Example: bulbourethral (Cowper’s) glands.
What is the structure of stratified cuboidal epithelium?
Stratified cuboidal epithelium has two or more layers of cells; cells in the apical layer are cube-shaped.
How are multicellular exocrine glands structurally classified?
Multicellular exocrine glands are structurally classified based on the branching pattern of the duct and the shape of the secreting portion.
Where is nonciliated pseudostratified columnar epithelium located?
It lines the epididymis, larger ducts of many glands, and parts of the male urethra.
Where can simple cuboidal epithelium be found in the body?
It covers the surface of the ovary, lines the anterior surface of the capsule of the lens of the eye, forms the pigmented epithelium at the posterior surface of the retina of the eye, lines kidney tubules and smaller ducts of many glands, and makes up the secreting portion of some glands such as the thyroid gland and ducts of some glands such as the pancreas.
What is the primary function of muscular tissue?
Muscular tissue is composed of cells specialized for contraction and generation of force, and it generates heat that warms the body.
What is the main structural difference between epithelial and connective tissues?
Epithelial tissue has many tightly packed cells with little or no extracellular matrix, while connective tissue has a large amount of extracellular material separating widely scattered cells.
What are the two general patterns of epithelial tissue arrangement in the body?
Epithelial tissue is arranged in two general patterns: covering and lining various surfaces, and forming the secreting portions of glands.
What is the apical surface of an epithelial cell?
The apical (free) surface of an epithelial cell faces the body surface, a body cavity, the lumen of an internal organ, or a tubular duct that receives cell secretions.
What are the characteristics of columnar cells?
Columnar cells are much taller than they are wide, like columns, and protect underlying tissues. Their apical surfaces may have cilia or microvilli, and they often are specialized for secretion and absorption.
What are tubular glands?
Glands with tubular secretory parts.
How do merocrine glands release their secretions?
Secretions are synthesized on ribosomes attached to rough ER, processed, sorted, and packaged by the Golgi complex, and released from the cell in secretory vesicles via exocytosis. Example: salivary glands and pancreas.
What functions do both keratinized and nonkeratinized stratified squamous epithelium serve?
Both types protect against abrasion, water loss, ultraviolet radiation, and foreign invasion, forming the first line of defense against microbes.
What are the functions of nonciliated simple columnar epithelium?
Secretion and absorption. Larger columnar cells contain more organelles and thus are capable of a higher level of secretion and absorption than cuboidal cells. Secreted mucus lubricates the linings of the digestive, respiratory, and reproductive tracts, and most of the urinary tract; it also helps prevent the destruction of the stomach lining by acidic gastric juice secreted by the stomach.
What are the secretions of endocrine glands called?
The secretions of endocrine glands are called hormones.
What structures might be found on the apical surface of epithelial cells?
The apical surfaces of epithelial cells may contain cilia or microvilli.
Describe a simple coiled tubular gland.
A gland where the tubular secretory part is coiled and attaches to a single unbranched duct. Example: sweat glands.
What happens to the cells of stratified squamous epithelium as they move toward the surface?
As cells move toward the surface and away from the blood supply in the underlying connective tissue, they become dehydrated, less metabolically active, and eventually die. Tough proteins predominate as the cytoplasm is reduced, and the cells become tough, hard structures.
What is the function of microvilli in nonciliated simple columnar epithelium?
Microvilli are fingerlike cytoplasmic projections that increase the surface area of the plasma membrane, thus increasing the cell’s rate of absorption.
What is a biopsy?
A biopsy is the removal of a sample of living tissue for microscopic examination to help diagnose disorders, especially cancer, and to discover the cause of unexplained infections and inflammations.
What are the main functions of the basement membrane in epithelial tissue?
The basement membrane anchors the epithelium to underlying connective tissue, forms a surface for epithelial cell migration during growth or wound healing, restricts passage of larger molecules between epithelium and connective tissue, and participates in blood filtration in the kidneys.
What allows epithelial tissue to constantly renew and repair itself?
A high rate of cell division allows epithelial tissue to constantly renew and repair itself by sloughing off dead or injured cells and replacing them with new ones.
What is a Papanicolaou test (Pap test) used for?
A Papanicolaou test (Pap test) is used to detect early changes in the cells of the female reproductive system that may indicate a precancerous condition or cancer.
What are acinar glands?
Glands with rounded secretory portions, also called alveolar glands.
What is the structure of simple cuboidal epithelium?
Simple cuboidal epithelium is a single layer of cube-shaped cells with a round, centrally located nucleus.
Describe the structure of nonciliated simple columnar epithelium.
Nonciliated simple columnar epithelium is a single layer of nonciliated columnlike cells with oval nuclei near the base of the cells. It contains columnar epithelial cells with microvilli at the apical surface and goblet cells.
How does nervous tissue function?
Nervous tissue detects changes inside and outside the body and responds by generating electrical signals called nerve action potentials that activate muscular contractions and glandular secretions.
How does epithelial tissue receive nutrients and remove wastes?
Epithelial tissue is avascular and relies on the blood vessels of adjacent connective tissue to bring nutrients and remove wastes through diffusion.
What is a simple gland?
A gland that does not branch.
What are tubuloacinar glands?
Glands that have both tubular and rounded secretory parts.
Describe a simple branched acinar gland.
A gland where the rounded secretory part is branched and attaches to a single unbranched duct. Example: sebaceous glands.
What are the two layers of the basement membrane?
The basement membrane commonly consists of two layers: the basal lamina and the reticular lamina.
What are the characteristics of cuboidal cells?
Cuboidal cells are as tall as they are wide and are shaped like cubes or hexagons. They may have microvilli at their apical surface and function in either secretion or absorption.
Describe a compound tubuloacinar gland.
A gland where the secretory portion is both tubular and rounded and attaches to a branched duct. Example: acinar glands of the pancreas.
What condition can cause the basement membrane to thicken, and what are the potential consequences?
In untreated diabetes mellitus, the basement membrane of small blood vessels thickens, which can lead to improper blood vessel function, potentially resulting in blindness and kidney failure.
Describe a compound acinar gland.
A gland where the secretory portion is rounded and attaches to a branched duct. Example: mammary glands.
To what class of glands do salivary glands belong?
Merocrine glands.
How do holocrine glands release their secretions?
The secretory product accumulates in the cytosol, and as the secretory cell matures, it ruptures and becomes the secretory product. Example: sebaceous glands.
Where is simple squamous epithelium commonly found?
cardiovascular and lymphatic systems (heart, blood vessels, lymphatic vessels) as endothelium,
forms the epithelial layer of serous membranes (peritoneum, pleura, pericardium) as mesothelium.
air sacs of lungs, glomerular (Bowman’s) capsule of kidneys,
inner surface of the tympanic membrane (eardrum).