What is the shape and function of simple squamous epithelium?
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Flattened, plate-like cells that allow rapid diffusion; found lining capillaries and blood vessels.
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What is the shape and function of simple squamous epithelium?
Flattened, plate-like cells that allow rapid diffusion; found lining capillaries and blood vessels.
What are the main specializations of the cell surface in epithelial tissues?
The presence of microvilli, cilia, or the protein keratin.
What term is used to describe the simple squamous epithelium that lines blood vessels?
Endothelium
What is the function of a brush border in simple columnar epithelium?
Increases surface area for absorption
What is the function of desmosomes in epithelial tissues?
They provide strong attachment between cells, particularly in tissues subject to abrasion and physical stress, such as skin and heart muscle.
What is a stratified epithelium?
An epithelium with two or more layers of cells.
What is the primary characteristic of simple squamous cells?
They have a centrally located nucleus and abundant but extremely thin cytoplasm.
What is atherosclerosis and how is it related to endothelial function?
Atherosclerosis is an arterial disease caused by the loss of proper endothelial function, common in patients with diabetes, hypertension, or other chronic conditions.
What is the role of goblet cells in the respiratory epithelium?
Goblet cells secrete mucus.
What are cilia and where are they found?
Cilia are microscopic projections of the apical cell membrane found lining parts of the respiratory tract and the uterine tubes in females.
What factors can affect cilia activity?
Common cold viruses, chemicals in tobacco smoke, barbiturates, old age, and cold air.
What forms a system in the body?
Organs combine to function within a particular system.
What is a brush border?
A brush border is formed by abundant microvilli and is visible under a light microscope.
How are epithelia classified?
Epithelia are classified based on the number of cell layers and the shape of the cells on the surface.
What is the function of goblet cells in the respiratory tract?
Goblet cells secrete mucus to trap particles in inspired air and moisten the surface of the respiratory tract.
What is stratified squamous epithelium?
Stratified squamous epithelium consists of multiple layers of cells with the top layer being flat, providing protection against abrasion.
What is a simple epithelium?
An epithelium with a single layer of cells.
What are the three shapes of cells found on the luminal surfaces of epithelia?
Squamous, cuboidal, and columnar.
Describe columnar cells.
Cells that are 2-3 times taller than they are wide, often involved in active transport or secretion.
How does smoking affect endothelial cells?
Toxic substances like nicotine open up intercellular junctions, allowing large molecules to pass through the vessel wall, leading to degenerative changes and vascular disease.
What is the metachronal wave?
The synchronous movement of cilia.
What is the function of connective tissue?
Connective tissue consists of cells, fibers, and extracellular matrix. It is a very diverse group of tissues.
What is the function of microvilli in epithelial cells?
Microvilli increase the surface area for absorption, especially in sites like the small intestine and proximal convoluted tubule of the kidney.
What is the polarity of epithelial tissue?
Epithelial tissue is polarized with a free, or apical surface, exposed to the outside, and an attached or basal surface, resting on the underlying basement membrane.
What is simple squamous epithelium?
Simple squamous epithelium is a single layer of flat cells that allows for easy diffusion and filtration.
What are stratified cuboidal and columnar epithelia?
Stratified cuboidal and columnar epithelia consist of multiple layers of cube-shaped or column-shaped cells, respectively, and are involved in protection and secretion.
What is the function of microvilli in simple columnar epithelium?
To increase the surface area.
What type of epithelium lines the bronchi?
Pseudostratified columnar epithelium
In which of the following locations would you find a brush border?
Small intestine
What is the role of tight junctions in epithelial cells?
They prevent the passage of molecules and ions through the space between cells and block the movement of integral cell membrane proteins between the apical and basolateral surfaces.
Describe the appearance and structure of simple squamous epithelium.
It is composed of a single layer of flattened, plate-like cells with a central nucleus, often referred to as 'pavemented epithelium' due to its appearance.
Describe the shape and function of simple columnar epithelium.
Cells are approximately twice as tall as they are wide; functions in secretion and absorption, found in the GI tract.
Where are simple squamous epithelia commonly found?
At sites where rapid diffusion of gas or fluid is necessary, such as alveoli of the lungs, or where a friction-free surface is required, such as walls of blood vessels.
What is transitional epithelium and where is it found?
Has two or more layers with the apical layer being cuboidal; changes shape as the epithelium is stretched, found lining the bladder.
What happens to the blood-brain barrier (BBB) during meningitis?
The meninges become disrupted and the BBB is breached, allowing antibiotics to penetrate more easily.
What are the four primary tissue types in the body?
Epithelial tissue, connective tissue, nervous tissue, and muscle tissue.
What are goblet cells and where are they commonly found?
Goblet cells are modified columnar cells that are abundant in the gastrointestinal and respiratory tracts.
What is unique about pseudostratified columnar epithelium?
It appears to be composed of multiple layers but is actually a single layer with all cells making contact with the basement membrane.
What is the function of the basal cells in stratified squamous epithelium?
They are mitotically active and replace the cells lost by 'wear and tear'.
What is the function of villi in the small intestine?
To increase the surface area for absorption.
What type of metaplasia occurs in the larynx and trachea after repeated physical, chemical, or thermal insult?
A change from pseudostratified columnar to stratified squamous epithelium.
What does the brush border of a simple columnar epithelium consist of?
Microvilli
What are the three criteria used to classify epithelial tissue?
The number of layers of cells, the shape of the cells lining the apical/luminal surface, and specializations of the cell surface.
Describe squamous cells.
Flat, scale-like cells that allow rapid diffusion but are fragile.
What is the structure and function of stratified squamous epithelium?
Has two or more layers with the apical layer being flattened and plate-like; provides protection, found in the esophagus and epidermis.
What are the functions of mesothelium?
Mesothelium provides a friction-free surface by secreting a watery fluid, facilitating movement of organs within a cavity.
What are the functions of endothelial cells?
Endothelial cells control the passage of substances in and out of the bloodstream, assist in forming the basement membrane, control blood pressure, assist in blood coagulation, secrete factors to break down blood clots, and are involved in angiogenesis.
What type of epithelium is found in the respiratory tract?
Pseudostratified columnar epithelium.
What is the function of muscle tissue?
Muscle tissue contracts to perform movements such as skeletal muscle movements, propulsion in the GI tract, and pumping blood in the heart.
What is epithelial tissue composed of?
Epithelial tissue is composed of one or more layers of cells with very little intercellular space.
What are the functions of epithelial tissues?
Epithelial tissues function in protection, absorption, secretion, and sensation.
How is stratified epithelium structured?
It is composed of two or more layers of cells.
What is the composition of stratified squamous epithelium?
It is composed of two or more layers of cells with the apical layer being squamous cells.
What is the primary function of the oesophageal epithelium?
Protection of underlying tissues from abrasion by the swallowed bolus of food.
What type of epithelium lines the bladder?
Transitional epithelium.
What term is used to describe a tumor originating in epithelial tissue?
Carcinoma
What is the purpose of gap junctions in epithelial cells?
They have tiny pores that allow the passage of small molecules between adjacent cells, enabling cells to respond to stimuli as a unit.
What is pseudostratified epithelium?
An epithelium that appears to have several layers of cells but actually has only one layer, with all cells making contact with the basement membrane.
Describe cuboidal cells.
Cells that are approximately as wide as they are tall.
What is the function of tight junctions in endothelial cells?
They form an almost impermeable barrier, such as in the blood-brain barrier.
Describe the structure and location of stratified columnar epithelium.
Has two or more layers with the apical layer being columnar; found in the male urethra.
What is mesothelioma?
Mesothelioma is a cancer of the mesothelium where cells become abnormal and divide without control, often linked to asbestos exposure.
What are the pathological implications of increased goblet cells and mucus production?
Increased goblet cells and mucus production occur in cystic fibrosis, asthma, and COPD.
What is the function of epithelial tissue?
Epithelial tissue covers and lines surfaces and cavities of the body (inside and out).
How many microvilli can be found per cell in high absorption sites?
Up to 3000 microvilli per cell.
What are epithelial cells?
Epithelial cells are cells that line the surfaces of the body, including skin, blood vessels, organs, and cavities.
What is simple cuboidal epithelium?
Simple cuboidal epithelium consists of a single layer of cube-shaped cells that function in secretion and absorption.
What is the characteristic shape of simple squamous cells?
Flattened form with flattened nuclei.
How do zonula adherens contribute to the stability of epithelial tissues?
They completely encircle each cell, providing stability by binding the cells together and linking the cytoskeletons of neighboring cells.
What are the key characteristics of simple squamous epithelium cells?
They appear as flattened, plate-like cells with a central nucleus, and their nuclei are sausage-shaped in longitudinal sections and round in transverse sections.
What role do endothelial cells play in acute inflammation?
They are activated by cytokines and express cell adhesion molecules for neutrophils.
What happens to endothelial cells in the presence of histamine?
They lose attachment to each other and retract, allowing fluid and proteins to diffuse out into the local tissues causing tissue swelling termed oedema.
Where can fenestrated endothelium be found?
In endocrine glands and the kidney.
Where is stratified cuboidal epithelium found and what is its structure?
Found in salivary glands and sweat glands; has two or more layers with the apical layer being cuboidal.
What is endothelium?
Endothelium is the simple squamous epithelium that lines the luminal surface of blood vessels, lymphatics, and the heart.
What is the function of mucus in the respiratory tract?
Mucus traps and eliminates microorganisms, dust, and other particles, protects cells from desiccation, and moistens inhaled air.
What stimulates the secretion of mucus from goblet cells?
Extracellular stimuli such as irritants in the intestine, dust, and smoke.
What forms a tissue?
A group of similar cells forms a tissue.
What is the basement membrane (BM) in epithelial tissue?
The basement membrane is a thin sheet composed of collagen and glycoprotein, produced partly by epithelial cells and partly by underlying connective tissue cells.
What is the unique shape of goblet cells attributed to?
The apical portion is goblet-shaped due to being filled with mucigen granules, while the basal portion contains the nucleus and other organelles.
What is simple columnar epithelium?
Simple columnar epithelium is a single layer of tall, column-like cells that function in absorption and secretion.
What is pseudostratified columnar ciliated epithelium?
Pseudostratified columnar ciliated epithelium appears to be stratified but is actually a single layer of cells with cilia, involved in secretion and movement of mucus.
How is the type of stratified epithelium determined?
By the type of cells present on the apical surface of the tissue.
What is the pathology related to the replacement of epithelial tissue?
Pathology related to the replacement of epithelial tissue involves conditions where the normal epithelial cells are replaced by abnormal cells, leading to diseases.
Where are columnar epithelia typically involved in active secretion and/or absorption?
In the small intestine (high absorption), stomach (high secretion), and gall bladder (high absorption).
What type of epithelium lines the luminal surfaces of the rugae in the stomach?
Simple columnar epithelium.
What type of metaplasia occurs in Barrett's oesophagus?
A change from oesophageal stratified squamous to gastric or intestinal simple columnar epithelium after repeated acid reflux.
What is the condition for a tumour to remain localized?
The tumour cells do not cross the basement membrane.
Where is simple cuboidal epithelium typically found and what is its function?
Found in the liver and kidneys; functions in secretion and absorption.
What is pseudostratified epithelium and where is it found?
Appears to have two layers due to varying cell heights but is actually a single layer; found in the respiratory epithelium lining the conducting part of the airway.
What is mesothelium?
Mesothelium is the simple squamous epithelium that lines the body cavities and is derived from embryonic mesoderm.
How can the blood-brain barrier (BBB) be opened?
By hypertension, hyperosmolitity, exposure to microwaves, radiation, infectious agents, brain trauma, ischemia, inflammation, increased skull pressure, hypercholesterolaemia, diabetes, or if not fully formed at birth.
What is the function of nervous tissue?
Nervous tissue carries information in the form of impulses throughout the body.
What forms an organ?
Various tissues form an organ.
What are the characteristics of epithelial tissue?
Epithelial tissue is formed from an uninterrupted layer of cells, covers all external and internal body surfaces, and forms boundaries between body compartments.
What is the function of goblet cells?
Goblet cells secrete mucus to moisten and protect the epithelial surfaces.
What are mesothelium and endothelium?
Mesothelium lines body cavities, while endothelium lines blood vessels and the heart.
What is the function of cilia in the respiratory tract?
To transport mucus and debris upwards towards the larynx where it can be swallowed.
Where is non-keratinized stratified squamous epithelium found?
In areas of the body not subjected to drying out but where abrasion occurs, such as the cornea, oral cavity, oesophagus, rectum, and vagina.
What are the primary functions of epithelial tissues?
Protect underlying tissues, synthesis and secretion, absorption of nutrients, excretion of waste substances, transport, sensation, and forming a friction-free surface.
Why is epithelial tissue avascular?
Because it has no blood supply; nutrients diffuse through the basement membrane from capillaries in the underlying connective tissue.
What are fenestrae in endothelial cells?
Gaps between individual endothelial cells that allow large molecules to move between the blood and surrounding tissues.
What does the blood-brain barrier (BBB) restrict and allow?
The BBB restricts potentially harmful substances but allows essential nutrients, oxygen, CO2, and some drugs like alcohol and general anesthetics.
What are some functions of epithelial tissues?
Cover external surfaces of the body, line closed spaces of the body, form specialized receptors, form secretory portions of exocrine glands and ducts, and act as selective barriers.
How is mucus transported upwards in the respiratory tract?
By the action of cilia which beat towards the larynx.
How are epithelial cells attached to one another?
Epithelial cells are tightly attached to one another by various types of intercellular junctions.
Where is simple columnar ciliated epithelium found and what is its function?
It is found in the uterine tubes, where cilia help sweep an ovum from the ovary to the uterus.
What is the blood-brain barrier?
The blood-brain barrier is a selective permeability barrier that protects the brain from harmful substances in the blood.
What is stratified squamous keratinized epithelium?
Stratified squamous keratinized epithelium has a layer of dead cells filled with keratin on the surface, providing a tough, protective barrier.
Where can cuboidal epithelium be commonly found?
Lining tubules and ducts, such as the collecting duct of the kidney, salivary glands, and the pancreas.
What is desquamation?
The process where the apical layers of stratified squamous epithelial cells are sloughed off and replaced by mitosis in the basal cells.
What are the surface modifications found in simple columnar epithelial cells?
Microvilli and goblet cells.
What is metaplasia in epithelial tissues?
A change (usually abnormal) from one distinctive tissue to another at a definite site after normal development is complete, implying a change in cell type (transdifferentiation).
What are intra-abdominal adhesions and how do they form?
Intra-abdominal adhesions are fibrous adhesions between opposing surfaces caused by insufficient removal of fibrin deposits due to damage to the mesothelium during surgical procedures.
What is Immotile Cilia Syndrome (Kartagener’s Syndrome)?
A condition where cilia fail to beat or beat less effectively, leading to mucus buildup and respiratory obstruction.
What is the significance of polarization in epithelial cells?
Polarization is particularly apparent in secretory and absorptive cells, reflecting the directional transport of material.
What are the three cell types found in pseudostratified columnar epithelium?
Basal cells, goblet cells, and columnar ciliated cells.
What are the specializations of the respiratory epithelium?
The respiratory epithelium has cilia and goblet cells that help trap and move particles out of the airways.
What type of cells line the arteries and veins?
Endothelial cells.
What is the height-to-width ratio of columnar cells?
The height of a columnar cell is usually 2-3 times its width.
What happens if an epithelial cell is stimulated to divide inappropriately?
A tumour can form.
What happens if tumour cells cross the basement membrane?
They enter the circulation and can metastasize (spread to other parts of the body).
What is a carcinoma?
A tumour originating in epithelial cells.
What type of epithelium lines the oesophagus?
Stratified squamous epithelium.
What type of epithelium lines the duodenum?
Simple columnar epithelium.
What is transitional epithelium?
Transitional epithelium is a type of stratified epithelium that can stretch and is found in the urinary bladder.
What is the shape of the deepest cells in stratified squamous epithelium?
Cuboidal or columnar.
What is the typical shape and nucleus position of cuboidal epithelial cells?
Cuboidal cells with a round, centrally located nucleus.
Where is keratinized stratified squamous epithelium found?
In the outermost layer of the skin.
What types of insults are epithelial tissues exposed to?
Mechanical damage (cuts and grazes), penetration (needles, insect bites), bacteria, fungi, and toxic chemicals.
In which tissues is carcinoma more likely to occur?
In tissues where brisk mitosis occurs, for example in the gut.