What are four examples of Special Cell Junctions?
1. Tight Junctions
2. Adhering Junctions
3. Desmosomes
4. Gap Junctions
Describe Tight Junctions
Tight Junctions or zonula occludens is a type of junctional complex. They are formed by claudin and occludin proteins, joining the cytoskeletons of the adjacent cells.
Describe the function of the Zonula Occludens (Tight Junctions)
They hold cells together, they block the movement of integral membrane proteins between the apical and basolateral surfaces of the cell. This aims to preserve transcellular transport. They prevent the passage of ions and molecules through the space between the cells.
Describe Desmosomes
1. Two disc like plaques connected across intercellular space.
2. Plaques of adjoining cells are joined by proteins called cadherins.
3. Proteins interdigitate into extracellular space
4. Intermediate filaments insert into plaques from cytoplasmic side.
Describe Gap Junctions
1. Passageway between two adjacent cells
2. They let smaller molecules move directly between neighboring cells
3. Cells are connected by hollow cylinders of protein
3 Features of the basal epithelial surface
1. Epithelial cells lie on a protein sheet called a basal lamina.
2. It acts as a filter and base on which regenerating epithelial cells can grow.
3. The basal lamina and some underlying reticular fibers form the thicker basement membrane.
Describe Connective Tissue
Connective Tissue serves a "connecting" function. It supports and binds to other tissues. Unlike epithelial tissue, connective tissue typically has cells scattered throughout an extracellular matrix. Derived from mesoderm.
What are four types of connective tissue?
1. Collagenous Fibers
2. Elastic Fibers
3. Reticular Fibers
4. Fibrous Connective Tissue
What are three types of specialized connective tissue?
1. Adipose
2. Cartilage
3. Bone
What is Marfan Syndrome?
An autosomal dominant genetic disorder of the connective tissue characterized by disproportionately long limbs, long thin fingers, a relatively tall stature, and a predisposition to cardiovascular abnormalities, specifically those affecting the heart valves and aorta.
What is the Pathogenesis of Marfan Syndrome?
Marfan Syndrome has been linked to a defect in the gene on chromosome 15 which encodes a glycoprotein called fibrillin - 1. Fibrillin is essential for the formation of the elastic fibers found in connective tissue.
What is Ehlers-Danlos Syndrome?
A group of rare genetic disorders affecting humans and domestic animals caused by a defect in collagen synthesis (Collagen I and Collagen III).
what is the percent of body fluid weight made up by water in the cells?
67%
What percentage of body fluid comprises the extracellular space?
33%
What percentage of extracellular fluid is composed of fluid in the blood?
20%
Describe the extracellular matrix
extracellular fluid as interstitial, or tissue, fluid, within a matrix of glycoproteins and proteoglycans. It consists of the protein fibers collagen and elastin. This fluid, derived from blood plasma, provides nutrients and regulatory molecules to the cells. The extracellular environment is supported by collagen and elastin protein fibers, which also form the basal lamina below epithelial membranes.
What are Integrins?
Integrins are a class of glycoproteins that extend from the cytoskeleton within a cell, through its plasma membrane, and into the extracellular matrix. By binding to components within the matrix they serve as adhesion molecules between cells and the extracellular matrix.
What are the two broad types of transport across the plasma membrane?
Carrier Mediated Transport and Simple Diffusion
What are the two types of Carrier Mediated Transport?
Facilitated Diffusion and Active Transport
What is Passive Transport?
The net movement of molecules and ions across a membrane from higher to lower concentration. It does not require metabolic energy. Passive transport includes simple diffusion, osmosis, and facilitated diffusion.
What is Active Transport?
The net movement across a membrane that occurs against a concentration gradient (to the region of higher concentration). Active transport requires metabolic energy (ATP) and involves specific carrier proteins.
Describe Simple Diffusion
1.The only form of transport that is not carrier mediated. Occurs down the electrochemical gradient, does not require ATP, and is therefore passive
What types of solutes can cross the cell membrane?
Hydrophobic or lipophilic
Describe the three characteristics of Carrier-Mediated Transport
1. Stereospecificity
2. Saturation
3. Competition
Describe Stereospecificity
For Example, D-Glucose (the natural isomer) is transported by facilitated diffusion, but the L-Glucose isomer is not. Simple diffusion, however, would not distinguish between the two isomers because it does not involve a carrier.
Describe Saturation
The transport rate increases as the concentration of the solute increases, until the carriers are saturated. The transport maximum is analogous to the maximum velocity in enzyme kinetics
Describe Competition
Structurally related solutes compete for transport sites on carrier molecules. For example galactose is a competitive inhibitor of glucose transport in the small intestine.
Define the basic structural and functional unit of life
Cell
All living organism are composed of
Cells
How many cells are in the human body?
50 to 100 trillion
What are the three main regions of the cell?
Plasma Membrane, Cytoplasm, Nucleus
What is the thin and flexible membrane of the cell which separates the intracellular from extracellular fluid?
Plasma Membrane
What is another name for the Plasma Membrane
plasmalemma
What are three things the membrane is composed of and what is embedded in the membrane?
Double layer of lipids; phospholipids, cholesterol, glycolipids; proteins are embedded
What is the most abundant lipid in the plasma membrane?
phospholipids
The heads of phospoholipids are (Hydrophilic/hydrophobic)
Hydrophilic
The tails of phospholipids are (Hydrophilic/hydrophobic)
Hydrophobic
What are the two types of membrane proteins?
Integral and Peripheral
What are the most abundant proteins in the membrane? (Most are transmembrane but some protrude from one side of the membrane) could act as a receptor.
Integral Proteins
What proteins are mostly on the cytoplasmic side and support that side by a network of filaments?
Peripheral Proteins
What is a short chain of carbohydrates (sugars) projected out from the external surface of glycoproteins or glycolipids called? what is its function?
Glycocalyx (Cell Coat); functions in cell to cell binding and recognition
What cells produce Glycocalyx?
Corneal epithelial surface cells
Three functions of the Plasma Membrane
1. Barrier against substances and forces outside cell
2. externally-facing proteins act as receptors and in cell to cell recognition
3. Acts in transport of substances into or out of cell
What type of barrier is the membrane considered?
Selective permeable
What is the Passive Process of movement?
Substances can pass freely through the lipid bilayer down their concentration gradient. No ATP needed
What is Diffusion?
Movement of small uncharged molecules like oxygen, CO2, and fat soluble molecules across the membrane
What is the Active Process of Movement?
Substances move against their concentration gradient from a lower to higher concentration. ATP is needed
What is Active Transport?
Most larger water soluble or charged molecules, such as glucose, amino acids, and ions are transported by a pump or carrier and involve the integral proteins
What is Vesicular or Bulk Transport?
Large particles and macromolecules pass through the membrane by this mechanism.
What are the two types of Bulk Transport?
Exocytosis and Endocytosis
What is Exocytosis?
Membrane-lined cytoplasmic vesicles fuse with the plasma membrane and release their contents to the outside of the cell.
What is an example of Exocytosis?
Mucus and Protein secretions from the glands in the body
What is Endocytosis?
Brings large molecules into the cell, through an initial infolding part of the plasma membrane that encloses them to form cytoplasmic vesicles. Clathrin Protein, found on the cytoplasmic side of the infolding, is responsible for deforming the membrane.
What are the three types of Endocytosis?
Phagocytosis, Pinocytosis, and Recptor-Mediated Endocytosis
What is Phagocytosis? (AKA Cell Eating)
A type of Endocytosis where parts of plasma membrane form pseudopodes and flow around large molecules such as bacteria or cellular debris and engulf it. By this way, a membranous vesicle, called a phagosome is formed.
What is the function of the Phagosome formed during Phagocytosis?
Phagosomes mostly fuse to the lysosomes for enzymatic breakdown of phagosomal contents. White Blood Cells typify such phagocytotic activity.
What is Pinocytosis? (AKA Cell Drinking)
Pinocytosis is fluid phase endocytosis, where a small infolding of the plasma membrane surrounds a small quantity of ECF containing dissolved molecules. This is the primary function of cells lining the small intestine, absorption of the nutrients.
What is Receptor-Mediated Endocytosis?
Receptor-Mediated Endocytosis is a selective mechanism. Specific molecules such as insulin and other hormones, enzymes, and LDLs are brought into the cells by first attaching to a receptor on the membrane before being taken into the cells in a protein coated vesicle. Contents are then released by binding to lysosomes and the receptors are recycled back into the plasma membrane. Viruses and some toxins use the same mechanism to enter cells.
What are LDLs?
Low Density Lipoproteins: Molecules that carry cholesterol in the blood to the body's cells
What is Familial Hypercholesterolemia?
An inherited disease in which the cells lack the receptors that bind cholesterol binding LDLs.
As a result, cholesterol cannot enter the cells and builds up in the blood, causing hypercholesterolemia and atherosclerosis which leads to stroke or myocardial infarction.
What is the Cytoplasm?
Cytoplasm is the cellular region between the nucleus and the membrane
What does the Cytoplasm consist of?
Cytosol, or cytoplasmic matrix which is a viscous fluid containing water, ions, and enzymes, inclusions containing stored nutrients and pigments and organelles.
What are Ribosomes?
Dark staining granules with no membrane. Ribosomes are the site of protein production.
What are the two subunits of Ribosomes?
Protein and Ribosomal RNA (rRNA, ribonucleic acid)
What is the function of the Ribosomes?
Free ribosomes make the protein used in cytosol. Ribosomes attached on the surface of rER make the proteins used for cell membrane or exported out of cell.
What is Translation?
Amino Acids on the ribosomes are linked together to form protein. This action is dictated by the DNA of the nucleus. Such instructions are carried to the ribosomes by messengers called messenger RNA (mRNA)
What is the Rough Endoplasmic Reticulum?
A ribosome-studded system of membrane-walled envelopes in cytosol, called cisternae. Ribosomes on the rER make proteins which enter the cisternae and are secreted by the cell in vesicles. Ribosomes also make the proteins of the cell membrane.
What makes the integral and peripheral proteins embedded in the cell membrane?
Ribosomes
What is the Smooth Endoplasmic Reticulum?
A network of membranous system of sacs and tubules in the cytosol. It has no ribosomes and is involved in the synthesis of lipids and steroids, lipid metabolism and drug detoxification.
What is the Golgi Apparatus?
A stack of 3-10 disc shaped envelopes or cisternae which are bound by a membrane. Cisternae have a cis (convex) and a trans (concave) face. It sorts the products of rER and packs them in membrane bound vesicles and sends them to their proper destination. Secretory granules and lysosomes also arise from the Golgi Apparatus.
What is the Mitochondria?
Rod like organelles covered by two membranes in the cytoplasm. The inner membrane is folded into projections called cristae. Mitochondria are the main energy generator of the cell and are the main site of ATP synthesis.
What are Lysosomes?
Spherical, membrane-walled sacs containing digestive enzymes called acid hydrolases. Lysosomes are site of intracellular digestion and they destroy (digest) deteriorated organelles and substances brought into the cells by vesicles. They fuse with phagosomes and empty their enzymes into the phagosomes, breaking down their contents. Phagocytic cells have a lot of lysosomes.
What is Tay-Sachs Disease?
Tay-Sachs Disease is a fatal genetic lipid storage disorder in which harmful quantities of a fatty substance called ganglioside GM2 build up in tissues and nerve cells in the brain. Infants lack specific enzymes in the lysosomes responsible for the break down of certain glycolipids. As a result, glycolipids accumulate in the cell membrane especially on neurons, resulting in mental retardation, blindness, and death within 1.5 years from birth.
What is Gaucher's Disease?
The lack of the glucocerebrosidase enzyme in lysosomes causes harmful substances to build up in the liver, spleen, bones, and bone marrow. The substances prevent cells and organs from working properly.
What is Type 1 Gaucher's Disease?
Most common form of Gaucher's Disease. Involves bone disease, anemia, an enlarged spleen, and thrombocytopenia. Type 1 affects both children and adults.
What is Type 2 Gaucher's Disease?
Type 2 usually begins in infancy with severe neurologic involvement. This form can lead to rapid, early death.
What is Type 3 Gaucher's Disease?
Type 3 may cause liver, spleen, and brain problems. Patients may live into adulthood.
What are some symptoms of Gaucher's Disease?
Bone pain and fractures, enlarged spleen, enlarged liver, lung disease, and seizures.
What are Peroxisomes?
Membrane-walled enzyme containing sacs. They contain oxidase and catalase enzymes. Oxidases use oxygen to neutralize aggressively reactive substances called free radicals, by converting them into hydrogen peroxide. Hydrogen Peroxide, although reactive and dangerous, is converted into water and oxygen by catalases which break down poisons like alcohol, phenol, and formaldehydes that have entered the body. Liver and Kidneys have many peroxisomes.
What is the Cytoskeleton?
A network of rods running throughout the cytosol to support the cellular structure and generate movements of the cell. There are 3 types of such cytoskeleton.
What are the three types of Cytoskeleton?
Microtubules, Microfilaments, and Intermediate Filaments.
What are Microtubules?
Cylindrical Structures made of tubulin proteins. They radiate out from the centrosome region close to the nucleus. They give the cell its shape and they organize the distribution and transport of various organelles within the cytoplasm.
What are Microfilaments?
AKA actin filaments. Fine filaments of contractile protein called actin. They are labile. Actin interacts with another protein called myosin, and generates contractile forces within the cell. It is involved in muscle contraction, and other types of cellular movements such as amoeboid movements and extension of psuedopods.
What are Intermediate Filaments?
Tough insoluble and stable protein fibers which act to resist tension placed on the cell.
What are the Centrosome and Centrioles?
The Centrosome is a spherical structure in the cytoplasm near the nucleus. It consists of an outer cloud of protein called matrix and an inner pair of centrioles. Matrix protein is involved in the elongation of microtubules and mitotic spindle of microtubules radiates from it in dividing cells
What are Cytoplasmic Inclusions?
Impermanent structures in the cytoplasm such as lipid droplets and glycogen containing glycosomes.
What are Centrioles?
Centrioles make up the core of the centrosome. These are paired cylindrical bodies perpendicular to one another and each composed of nine triplets of microtubules. They organize a microtubule network during mitosis to form the spindle and asters. They also form the bases of cilia and flagella.
What is the Nucleus?
The Nucleus is the control center of the cell and contains genetic materials (DNA), which directs the cell's activities by providing instructions for protein synthesis. Most cells have one nucleus in the center. Some have multiple nuclei e.g. skeletal muscle, however mature red blood cells have no nucleus (annucleate) at all.
What are the three main parts of the nucleus?
1. Nuclear Envelope
2. Chromatin and Chromosomes
3. Nucleoli
What is the Nuclear Envelope?
Surrounds the nucleus and has pores and is continuous with the endoplasmic reticulum
What is the Nucleolus?
A dark staining body within the nucleus. It contains parts of chromosomes and is cell's ribosome producing machine (Has genes that code for rRNA)
What is Chromatin?
Chromatin is the granular thread like material in the nucleus composed of DNA (Deoxyribonucleic acid) and Histine Proteins. DNA constitute the genes.
What is Transcription?
Genetic code is copied onto mRNA
What is DNA?
DNA molecule in chromatin is a double helix of nucleotide molecules. Nucleotides consist of sugar, phosphate, and one of four bases: Thymine (T), adenine (A), cytosine (C), or guanine (G), which bind to hold the DNA helix together like a ladder. DNA helix wraps around clusters of eight spherical proteins called histones, which regulate gene expression and transcription. Each cluster of DNA and histones is called a nucleosome.
What are Chromosomes?
A Chromosome contains a single, very long, molecule of DNA. There are 46 chromosomes in a typical human cell. Chromatin is distributed in chromosomes. During cell division, the chromatin is highly coiled, making the chromosomes appear as thick rods.
What are the two major periods of the Cell Life Cycle?
Interphase and Cell Division
What is Interphase?
the cell grows and carries on its usual activities
What is Cell Division (Mitotic phase)?
During this period, the cell divides into two cells. Cell division is essential for growth and repair of the body.
What are the three phases of Interphase?
Gap 1 (G1), Synthetic (S), and Gap 2 (G2)
What happens in the G1 Phase?
Cells are active and grow vigorously and centrioles start to replicate.
What happens in the S Phase?
DNA replicates itself for the future two daughter cells having identical genetic material
What happens in the G2 Phase?
Enzymes needed for cell division are synthesized, centrioles finish replication and cell gets ready to divide.
What are the four stages of Cell Division or Mitosis?
Prophase, Metaphase, Anaphase, and Telophase.
What happens in the Prophase?
Asters (stars) are formed; these are microtubule arrays, extending from the centrosome. Chromosomes are formed from coiling and condensation of the chromatin threads. (Each chromosome has 2 identical chromatin threads, now called chromatids: The chromatids are held together by a centromere and a protein complex called cohesin) Nucleoli disappear, centriole pairs separate, nuclear envelope fragments. Microtubules disassemble and are newly assembled to form mitotic spindles which lengthen and push the centrioles farther apart to the poles of the cell (some of these spindles are attached to chromosomes and are called kinetochores; others are called polar spindles)
What happens in Metaphase?
Chromosomes cluster at the middle of cell, to form a metaphase plate. Separase, an enzyme which cleaves cohesin, starts to separate the chromatids.
What happens in the Anaphase?
The V-Shaped chromatids are pulled apart by the kinetochore spindles to become the chromosomes of daughter cells, and the polar spindles still push against each other to elongate the cell. This stage only lasts a few minutes.
What happens in the Telophase?
This phase is like prophase in reverse. Chromosomes at the opposite ends of the cell uncoil and resume extension of the chromatin. Nuclear envelope forms by rER. Nucleoli appear. For a short period, the cell has 2 nuclei until it is completely separated by the process of cytokinesis.
What is Meiosis?
Meiosis is a specialized version of mitosis that occurs only in the production of gametes. It consists of 2 divisions that result in the formation of four gametes, each containing half the amount of DNA (1N) found in normal somatic cells. (46 Single Chromosomes, 2N)
What happens in Meiosis I?
Synapsis: Pairing of 46 homologous duplicated chromosomes
Crossing Over: large segments of DNA are exchanged.
Alignment: 46 homologous duplicated chromosomes align at the metaphase plate
Disjunction: 46 homologous duplicated chromosomes separate from each other; centromeres do not split
Cell Division: two secondary gametocytes (23 duplicated chromosomes, 2N) are formed.
What happens in Meiosis II?
Synapsis is absent, Crossing Over is absent, Alignment of 23 duplicated chromosomes at the metaphase plate. Disjunction of 23 duplicated chromosomes to form 23 single chromosomes. Centromeres split.
Cell Division: four gametes (23 single chromosomes, 1N) are found.
What are 4 diseases that can result due to a chromosomal problem?
Aneuploidy, abnormal number of chromosomes, can be trisomy or monosomy. Down Syndrome (trisomy 21), Klinefelter Syndrome (XXY), and Turner Syndrome (X0) is monosomy.
What are Gametes?
Gametes contain 23 single chromosomes (22 autosomes and 1 sex chromosome) and 1N amount of DNA. The term haploid is classically used to refer to a cell containing 23 single chromosomes. Female gametes contain only the X sex chromosome. Male Gametes contain either the X or the Y sex chromosome; therefore, the male gamete determines the genetic sex of the individual.
What is Aging?
Aging is complex and may involve cell damage due to free radicals as a result of normal cell metabolism or cell injury due to radiation and chemical pollutants.
What is the Mitochondrial Theory of Aging?
Involves a decrease of energy production by radical-damaged mitochondria which weakens and ages the cell. Vitamins C and E act as antioxidants and prevent excessive production of free radicals. The same is true with caloric intake restriction due to lowering the metabolic rate which slows aging.
What are the Genetic theories of aging?
these theories propose that aging is programmed into our genes (senescence)
What is Apoptosis? (Programmed Cell Death)
Apoptosis is the method whereby cells are removed from tissues in an orderly fashion as a part of normal maintenance or during development.
What are the morphological features of cells that undergo apoptosis?
Chromatin condensation, breaking up of the nucleus, and the plasma membrane. The cell shrinks and is fragmented into membrane-enclosed fragments called apoptotic bodies.
What are the signals that induce apoptosis?
Certain cytokines, such as tumor necrosis factor (TNF), may also activate caspases that degrade regulatory and structural proteins in the nucleus and cytoplasm, leading to the morphological changes characteristic of apoptosis.
What happens when there are defects in apoptosis?
Too much apoptosis causes extensive nerve cell loss in Alzheimer Disease and Stroke. Insufficiency of Apoptosis has been linked to cancer and autoimmune disease.
What is Cancer?
A cell mass which divides and multiplies abnormally; it is also called a neoplasm. Neoplasms are defined as benign or malignant.
What is a Benign Neoplasm?
A benign neoplasm or tumor is a local mass, remains compacted, often encapsulated, grows slowly and seldom kills the host.
What is Malignant Neoplasm?
Malignant neoplasm or cancer is a mass which is not capsulated and grows rapidly. Cells here are immature and they invade their surrounding. These give metastasis (invading other tissues) by means of lymphatics and/or blood.
What are Oncogenes?
Oncogenes are the result of mutations of certain regulatory genes, called protooncogenes, which normally stimulate or inhibit cell proliferation and development. Genetic accidents or viruses may lead to the formation of oncogenes. Oncogenes dominate the normal alleles (Proto-Oncogenes), causing deregulation of cell division, which leads to a cancerous state. Bladder Cancer and acute myelogenous leukemia are caused by oncogenes.
What are Tissues?
Tissues are a collection of structurally similar cells with related function. The entire body is composed of only four major types of tissues.
What are the four major types of tissue?
1. Muscle
2. Nervous
3. Epithelial
4. Connective Tissues
What are Organs?
Grouping of the four types of tissues into anatomical and functional units
What are Organ Systems?
Groups of Organs grouped together through common function
What is Muscle Tissue?
Muscle is contractile tissue of the body and is derived from the mesodermal layer of embryonic germ cells. It is classified as skeletal, cardiac, or smooth muscle, and its function is to produce force and cause motion, either locomotion or movement within internal organs.
What is Skeletal Muscle?
Skeletal Muscle is a type of striated muscle, usually attached to the skeleton. Skeletal muscles are used to create movement, by applying force to bones and joints; via contraction.
What is Smooth Muscle?
Smooth Muscle is found within walls of organs and structures such as the esophagus, stomach, small intestine, bronchi, uterus, urethra, bladder, and blood vessels, and unlike skeletal muscle, smooth muscle is not under conscious control.
What is Cardiac Muscle?
Cardiac Muscle is also an "involuntary muscle" but is a specialized kind of muscle found only within the heart.
What is Nervous Tissue?
Tissue that is specialized to react to stimuli and to conduct impulses to various organs in the body which bring about a response to a stimulus.
What is Nerve Tissue made of?
Specialized nerve cells called Neurons
What are Neurons?
Nerve cells that are easily stimulated and transmit impulses very rapidly
What are Nerves made of?
Many nerve cell fibers (neurons) bound together by connective tissue. A sheath of dense connective tissue, called the epineurium surrounds the nerve
What is the Perineurium?
The Epineurium penetrates the nerve and forms the Perineurium which surrounds bundles of nerve fibers. Blood vessels of various sizes can be seen in the Epineurium.
What is the Endoneurium?
Consists of a thin layer of loose connective tissue, surrounds the individual nerve fibers.
What are the eight functions of Epithelial Tissue?
1. Protection
2. Sensation Sensory (Senses)
3. Secretion in Glands (Secretion of Hormones, enzymes)
4. Absorption (such as in the Small Intestine)
5. Excretion (Such as in the Kidneys or Sweat Glands)
6. Diffusion (Such as in the lungs or capillary walls)
7. Cleaning (such as removing dust particles in the Throat)
8. Reduces Friction (such as in blood vessels)
What are the three shapes of Epithelial Tissue and how are they further divided?
1. Squamous (Flat)
2. Cuboidal (Cube like)
3. Columnar (Tall and Rod like)
Epithelial tissue is further divided into either simple (single layer of cells), Stratified (Multiple layers), or Pseudostratified (usually only in one type: Pseudostratified columnar, single layer, but position of cell nucleus gives appearance of stratified)
Describe a simple squamous epithelial tissue
Flat, cell nuclei appear as bumps. Gases and other substances can easily diffuse across squamous cells to the underlying basement membrane, and because of their smooth surface, liquids can easily flow over them. Simple Squamous epithelial tissues are usually seen lining body cavities and capillaries to reduce friction, as well as lining the alveoli to assist in the gas exchange.
Describe the location and function of a simple cuboidal epithelium
Cuboidal epithelium are located in glands and in the lining of kidney tubules as well as the ducts of glands. They also constitute the germinal epithelium which produces the egg cells in the female ovary and the sperm cells in the male testes. Their function is secretion and absorption.
Describe the location and function of a simple columnar epithelium
Columnar epithelium form the lining of the stomach and intestines. Some columnar cells are specialized for sensory reception such as in the nose, ears, and taste buds of the tongue. Goblet cells (unicellular glands) are found between the columnar epithelial cells of the duodenum. Their function is to secrete mucus or slime, a lubricating substance which keeps the surface smooth.
Describe the function and location of pseudostratified columnar epithelium
Pseudostratified columnar epithelium are located in the ducts of large glands, ciliated variety lines the trachea and most of the upper respiratory tract. Their function is secretion of mucus.
Describe the function and location of a stratified cuboidal epithelium
Stratified cuboidal epithelium are located in the ducts of sweat glands and the male urethra. Their function is protection.
Describe the function and location of a stratified columnar epithelium
Stratified columnar epithelium are found in small amounts in the male urethra, and in the large ducts of some glands. Their function is protection and secretion.
Describe the function and location of stratified squamous epithelium
Stratified squamous epithelium are located in the vagina. Their function is protection.
Describe the location and function of transitional epithelium
Transitional epithelium lines the ureters, bladder, and part of the urethra. Its function is to stretch readily and permit the distension of the urinary organs by containing urine.
What are the two types of glands and what is their primary function?
Endocrine and Exocrine. These glands secrete various products such as hormones, enzymes, metabolites, and other molecules.
Describe Exocrine glands
Exocrine glands are glands that retain ducts to body surfaces. products of these cells collect in the duct of the gland and flow toward the surface to which the duct is in contact. Goblet cells are exocrine glands. Multicellular exocrine glands are classified by the structure of their ducts as simple or compound, and by the structure of their secretory units as tubular, alveolar (acinar), or tubuloalveolar.
Describe Endocrine glands
Endocrine glands are ductless glands. Since they are ductless, their product is released across the cell membrane into interstitial spaces around the cells. The product is then diffused into other cells. Endocrine glands primarily secrete hormones which enter the circulation and reaches the target tissue to have their effects.
What does the exocrine part of the Pancreas produce?
Produces enzymes responsible for food digestion and breakdown
What does the endocrine part of the Pancreas produce?
Produces insulin and glucagon and other hormones.
What are the three different modes of Secretion in the exocrine glands?
1. Merocrine
2. Apocrine
3. Holocrine
Describe the Merocrine Method
Forms membrane bound secretory vesicles internal to the cell. These are moved to apical surface where the vesicles coalesce with the membrane on the apical surface to release the product. Most glands release their product this way.
Describe the Apocrine Method
The apical portions of the cells are pinched off and lost during the secretory process. This results in a secretory product that contains a variety of molecular components including those of the membrane. Mammary glands release their products in this manner.
Describe the Holocrine Method
This method involves death of the cell. The secretory cell is released and as it breaks apart, the contents of the cell become the secretory product. This mode of secretion results in the most complex secretory product. Some sweat glands located in the axillae, pubic areas, and around the areoli of the breasts release their products in this manner. Sebaceous glands are also of this type.
What are three factors holding epithelial cells together?
1. Adhesion proteins link plasma membranes of adjacent cells
2. Contours of adjacent cell membranes
3. Special cell junctions