Epithelial cells 17 + 18 Flashcards
stuff bout epithelial cells
What are Glia?
Non-neuronal support cells of the nervous system
Literally called brain glue
What are astrocytes?
- Sub-type of glial cells that make up the majority of cells in the CNS
- Forms part of the BBB
- Has lots of branches called processes that can touch thousands of neurons
- Feed neurons by shuttling nutrients from blood vessels to neurons
- Help buffer concentrations in the brain to regulate action potentials
What is the BBB?
Blood brain barrier
- Complex that surrounds most of the vessels of the brain
- Acts as a barrier between the blood stream and extracellular space of the brain, allowing only certain substances like water, oxygen and small lipid-soluble substances to pass through
- Used to prevent harmful things from crossing from the circulatory system into the brain.
What are Oligodendricytes?
- Type of myelinating glia
- Myelinates multiple axons in the CNS
- Doesn’t regenerate unlike schwann cells
- Has no outer neurolemma
- ## Does have outer plasms membrane
What are microglia?
- Type of phagocytic glia
- When activated, triggers immune system
What are ependyma>
- Epithelial cells that line the ventricular cells of the brain and central canal or spinal cord
- ## Has cilia to help movment of CSF
Name the different protection of the CNS
- Bone
- BBB
- Meninges
- Blood-CSF barrier
What is the venticular system in the brain?
- FLuid-filled space within the brain and spinal cord
- Used as shock absorber, bathes cells of CNS, maintains normal ionic composition
- CSF circulates within the ventricles - secreted by choroid plexus
What secretes CSF?
Choroid plexus
Roles of CNS:
- Responds and adapts to external and internal changes to the environment
- Co-ordinates all activities of the body
- Memory
- Maintains body functions
Roles of PNS:
- Detect different peripheral sensory information and sends to the brain for processing ie somatic (skin, joints, muscle), special (sight, hearing, balance, smell, taste) and visceral (from internal organs)
- Send directions from brain to target
Epithelia cells that line the ventricular system of the brain and spinal cord
Ependymal cells
Most abundant glial cells in the CNS and forms end feet around capillaries associated with the BBB
Astrocytes
Processes that receive incoming signals on the neuron
Dendrites
Glial cells that myelinate peripheral axons
Oligodendocytes
Bundles of axons in the CNS
Tracts
Myelin sheaths around axons within the CNS are formed by the what cells
Oligodendrocytes
Choroid plexus secretes this fluid into the ventricular system of the brain
Cerebrospinal fluid
Cell bodies cluster in the peripheral nervous system
Ganglia
What is the part of the PNS that controls voluntary movement
Somatic
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What are the primary functions of epithelial tissues?
Secretion, absorption, protection, and sensory perception.
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How are epithelial tissues classified by layers?
Simple (one layer), pseudostratified (appears layered but isn’t), stratified (multiple layers).
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Name the cell shapes used to classify epithelia.
Squamous (flat), cuboidal (cube-shaped), columnar (tall and rectangular)
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What surface specializations can epithelial cells have?
Cilia (movement), microvilli (absorption), keratin (protection).
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What is the basement membrane, and what does it do?
A thin, non-vascularized layer that anchors epithelium to connective tissue, providing support and acting as a barrier.
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What are the main components of the basement membrane?
Laminin (cell-binding) and collagen IV (structural support).
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What are the two main components of connective tissue?
Cells (e.g., fibroblasts, adipocytes) and extracellular matrix (ECM).
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What is the function of fibroblasts?
They produce fibers (collagen, elastin) and the ECM.
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What are proteoglycans, and why are they important?
Molecules with a protein core and multiple GAG chains that trap water, resist compression, and form gels.
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Name two examples of GAGs and their functions.
Chondroitin sulfate (resists compression in cartilage) and hyaluronate (lubricates joints).
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What is the structure of collagen?
Three alpha-chains form a triple helix, which assembles into fibrils and fibers.
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What is the function of collagen in connective tissues?
Provides tensile strength and resists stretching forces.
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What is elastin, and where is it found?
The main component of elastic fibers, found in skin, blood vessels, and lungs.
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What does elastin do?
Provides elasticity, allowing tissues to stretch and return to their original shape.
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What are the three main layers of the skin?
Epidermis (outer keratinized layer), dermis (dense connective tissue), hypodermis (loose connective tissue and fat).
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What is the stratum corneum, and why is it important?
The outermost layer of the epidermis; it prevents water loss and protects against microbes.
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What are the two main pathways for drug delivery through the skin?
Transepidermal (paracellular and transcellular) and transappendageal (via sweat glands or hair follicles).
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What properties make a drug suitable for transdermal delivery?
Low molecular weight (<500 Da), lipophilicity, and low daily dose requirements (<2 mg).
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What are the main types of cell junctions?
Tight junctions, adherens junctions, desmosomes, hemidesmosomes, and gap junctions.
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What is the function of tight junctions?
Create a barrier to restrict molecule passage and maintain cell polarity.
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What are the three components of the cytoskeleton?
Microfilaments (actin), intermediate filaments (keratin), and microtubules (tubulin).
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What is the BBB, and why is it important?
A selective barrier that protects the brain by preventing most substances from crossing.
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Name two drugs that can cross the BBB.
Morphine (pain relief) and L-DOPA (Parkinson’s disease).
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What are some strategies to deliver drugs across the BBB?
Design analogs, use the Trojan horse method, disrupt the barrier, or use nanoparticles.
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Name a disease treated with a drug designed to cross the BBB.
Parkinson’s disease, treated with L-DOPA.
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What are the main layers of the skin?
Epidermis: Outer layer, keratinized for protection.
Dermis: Middle layer, dense connective tissue with nerves and vessels.
Hypodermis: Inner layer, loose connective tissue with fat.
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What is the stratum corneum, and why is it important?
The outermost layer of the epidermis made of dead, keratinized cells; it prevents water loss and protects against microbes.
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What are keratinocytes?
The main cell type in the epidermis that produces keratin, aiding in waterproofing and barrier formation.
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What is paracellular drug delivery?
Drugs pass between cells through tight junctions, a route for small, water-soluble molecules
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What is transcellular drug delivery?
Drugs pass directly through cells, crossing the lipid-rich plasma membranes.
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What is the role of a transdermal patch?
Delivers medication through the skin for continuous, controlled release into the bloodstream.
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What properties must drugs have for transdermal delivery?
Low molecular weight (<500 Da).
Lipophilic (fat-soluble).
Effective at low doses (<2 mg/day).
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What are tight junctions, and where are they found?
Tight junctions create a barrier to prevent the movement of substances; they are critical in the blood-brain barrier. Found in epithelial and endothelial cells
of the bbb, lining of intestines etc
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What is the function of desmosomes?
Desmosomes connect intermediate filaments of adjacent cells, providing mechanical strength.
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How do gap junctions allow communication?
They form channels between cells, enabling ions and small molecules to pass directly.
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What are hemidesmosomes?
Structures that anchor epithelial cells to the basement membrane, connecting to intermediate filaments.
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Functions of Epithelial Tissues
- Secretion: Release of substances like mucus, enzymes, and hormones (e.g., glands).
- Absorption: Uptake of nutrients and water, primarily in the digestive system (e.g., intestinal lining).
- Protection: Acts as a barrier against physical damage, pathogens, and dehydration (e.g., skin).
- Sensory Perception: Specialized epithelia detect stimuli (e.g., taste buds, olfactory epithelium).
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What is the function of the ground substance in the ECM?
It fills the space between cells, traps water, and allows the diffusion of nutrients and waste.
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What are proteoglycans?
Large molecules with a core protein linked to glycosaminoglycan (GAG) chains that provide hydration and compression resistance.
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What are glycosaminoglycans (GAGs)?
Long, unbranched polysaccharide chains that trap water to form a hydrated gel, aiding in shock absorption.
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What are fibroblasts?
Fibroblasts are cells that produce ECM components, including collagen and elastin fibers.
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What are adipocytes, and what do they do?
Adipocytes are fat-storage cells found in connective tissue, providing energy reserves, insulation, and cushioning.
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What are mast cells, and what is their function?
Mast cells are immune cells in connective tissue that release histamine and other chemicals during allergic reactions.
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How do proteoglycans contribute to ECM structure?
Their highly hydrophilic nature attracts water, forming gels that resist compressive forces.
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How are keratinocytes replaced?
6 marks
The process by which keratinocytes are replaced involves the following steps:
Stem Cell Division: Stem cells in the basal layer (stratum basale) of the epidermis divide by mitosis to produce new keratinocytes.
Migration: The newly formed keratinocytes move upwards through the layers of the epidermis as they are pushed by the formation of more cells beneath them.
Differentiation: As keratinocytes migrate, they undergo differentiation, synthesizing keratin and other proteins, which contribute to the skin’s protective properties.
Formation of the Stratum Corneum: The keratinocytes reach the stratum corneum (outermost layer) and transform into dead, flattened cells called corneocytes, which are embedded in a lipid matrix.
Shedding: The corneocytes are eventually shed from the skin surface in a process called desquamation, maintaining the skin’s protective barrier.
Continuous Renewal: This cycle repeats constantly, with the entire epidermis being renewed approximately every 4–6 weeks.
L18: Cell cytoskeleton
What is the main function of epithelial tissues?
Epithelial tissues function in secretion, absorption, protection, and sensory perception.
L18: Cell cytoskeleton
How are epithelial tissues supported?
Epithelial tissues are supported by a basement membrane and connective tissue.
L18: Cell cytoskeleton
What are the three morphological classifications of epithelia?
Epithelia are classified based on the number of cell layers (simple, pseudostratified, stratified), cell shape (squamous, cuboidal, columnar), and surface specializations (e.g., cilia, microvilli, keratin).
L18: Cell cytoskeleton
What is the extracellular matrix (ECM), and why is it important?
The ECM is a network of proteins and other molecules crucial for tissue integrity, cell adhesion, and resistance to stress. In animals, it includes basement membranes and interstitial matrix.
L18: Cell cytoskeleton
What is the basement membrane, and what are its components?
The basement membrane is a thin layer underlying epithelial tissues, composed of laminin and collagen IV, which anchor epithelial cells.
L18: Cell cytoskeleton
What are the main components of connective tissue?
Connective tissue consists of cells (e.g., fibroblasts, adipocytes, mast cells) and extracellular matrix, including ground substance and fibers like collagen and elastin.
L18: Cell cytoskeleton
How does the structure of collagen contribute to its function?
Collagen forms triple-helical strands that assemble into fibrils and fibers, resisting stretching forces and providing structural support in tissues.
What is the role of elastin in connective tissue?
Elastin provides resilience and elasticity, allowing tissues like blood vessels, lungs, and skin to stretch and recoil.
Describe the structure and function of the epidermis.
The epidermis is a stratified squamous keratinized epithelium with layers including the basal, spinous, granular, and stratum corneum. It provides a protective barrier and prevents water loss.
What is terminal differentiation in keratinocytes?
Terminal differentiation involves keratin aggregation, nuclear degradation, lipid extrusion, and formation of the cornified envelope, resulting in the protective stratum corneum.
What are tight junctions, and what are their roles?
Tight junctions form a selective permeability barrier and maintain epithelial cell polarity. Components include claudin and occludin proteins.
What is the blood-brain barrier (BBB), and why is it significant?
The BBB is a highly selective permeability barrier formed by capillary endothelial cells, basement membrane, and astrocytes. It prevents most drugs and toxins from entering the brain.
How do drugs cross the blood-brain barrier?
Drugs cross via the transcellular pathway (lipid-soluble molecules, transporters, receptor-mediated endocytosis) or paracellular pathway (small water-soluble molecules).
What is the role of microfilaments in cell migration?
Microfilaments, composed of actin, facilitate cell migration by forming lamellipodia and focal adhesions at the leading edge, creating traction for movement.
How do microtubules contribute to cell division?
Microtubules form the mitotic spindle, which separates duplicated chromosomes during cell division. They also reorganize after division to maintain cell structure.
What are beta-blockers, and how do they work?
Beta-blockers, like propranolol, are adrenergic receptor antagonists that block adrenaline’s effects, used to treat conditions like hypertension and arrhythmias.
What is pemphigus, and how does it affect epithelial integrity?
Pemphigus is an autoimmune disease targeting desmogleins, leading to loss of keratinocyte adhesion, compromised epidermal integrity, and skin blistering.
desmogleins are a type of desmosomes
