Histology Flashcards
Who is the father of histology?
Marie François Xavier Bichat
What five things compose the cell and their percentage?
- Water (80%)
- Protein (15%)
- Lipid (2.5%)
- Carbohydrate (1.5%)
- Inorganic (1.0%)
The five common features to all eukaryotic cells
- An outer membrane
- An inner cytosol
- A cytoskeleton
- Membrane-bound organelles within the cytosol.
- Inclusions
What is the plasma membrane and its function?
It is a bimolecular layer of amphipathic phospholipid molecules with their hydrophilic heads at the outer and inner surfaces and their hydrophobic fatty acid chains facing toward the middle of the two layers.
Separates the cytoplasm from the extracellular environment.
Draw the amphipathic phospholipid and what it is made of
-Polar hydrophilic region of choline and phosphate
-Non-Polar hydrophobic fatty-acid chain
What five things can integral proteins be?
These include receptors, channels, transporters, enzymes, and cell attachment proteins.
The cell membrane is solid. True or false?
Nope, it is fluid, therefore it can change shape easily.
Are membrane proteins distributed equally within the cell membrane?
No, membrane proteins can diffuse laterally in the cell membrane, but many are anchored
What is the plasma membrane permeable and impermeable to?
Highly permeable to water, oxygen, and small hydrophobic molecules.
Virtually impermeable to charged ions (e.g., Na+)
What appearance does the plasmalemma have in the microscope?
Trilaminar appearance
What is the inner cytosol, and what does it contain?
A solution of proteins, electrolytes & carbohydrates. It has both fluid and gel-like properties.
What two structures does the cytosol have within?
Organelles and Inclusions
What are organelles?
Organelles are small, intracellular ‘organs’ with a specific function and structural organization.
What are the six organelles, and what are their functions?
- Mitochondria - (energy production)
- Rough endoplasmic reticulum - (protein synthesis)
- Smooth endoplasmic reticulum - (cholesterol & lipid synthesis/detoxification)
4.Golgi apparatus - (modification & packaging of secretions) - Lysosomes – (hydrolytic enzymes for intracellular digestion)
- Nucleus – (contains genetic code)
What are inclusions and some examples of them?
They represent components that have been synthesized by the cell itself…
Pigment, glycogen stores, lipid droplets, pre-secretion product
Or taken up from the extracellular environment.
Endocytotic vesicle.
What is the cytoskeleton made of?
Maintained by a set of filamentous cytosolic proteins, the cytoskeletal proteins
What are the three main classes of filaments, their size, and composition?
-Micro-filaments
(7 nanometres in diameter) are composed of
the protein actin.
-Intermediate filaments
(>10 nanometres in diameter) are composed of six main proteins, which vary in different cell types
-Microtubules
(25 nanometres in diameter) are composed of two tubulin proteins
What unique ability do microfilaments have?
Actin molecules can assemble into filaments and later dissociate, making them very dynamic cytoskeletal elements
What do the intermediate filaments do, and how many types are there?
Bind elements intracellularly together and to the plasma membrane. More than 50 types, but they are divided into classes.
What intermediate filaments form in the cytoplasm?
A network
What are microtubules composed of?
Hollow tubule is composed of two types of tubulin subunits, α & β, in an alternating array.
Where do microtubules originate from, and what proteins are included?
Originate from a special organizing center called the centrosome.
Include stabilizing proteins: microtubule-associated proteins (MAPS)
What type of filament can be assembled and disassembled?
Microfilaments
In what three structures are microtubules essential?
Cilia, flagella, and the mitotic spindle.
What do microtubules serve as, and what two proteins attach to the microtubules?
Microtubules serve as the ‘motorway’ network of the cell. Two proteins, dynein, and kinesin attach to the microtubules and move along them. They associate with the membranes of organelles and vesicles and ‘drag’ them along the microtubule.
What is kinesin, and where does it move?
Kinesin is an ATPase that moves toward the cell periphery.
What is dynein, and where does it move?
Dynein is an ATPase that moves toward the cell center.
What proteins are very important in the movement of components in cells with long processes, for example, the very long axonal process of many neurons?
Kinesin and dynein
What is the nucleus enclosed by and composed of?
The nucleus is enclosed by a nuclear envelope, composed of an inner and an outer nuclear membrane with nuclear pores providing continuity with the cytoplasm.
What is the outer membrane of the nucleus studded with, and what is it continuous with?
The outer nuclear membrane is studded with ribosomes and is continuous with the cytoplasmic rough endoplasmic reticulum.
What does the nucleus contain, and what three critical processes occur?
The nucleus contains chromosomes.
It is the location of RNA synthesis.
Both mRNA and tRNA are transcribed in the nucleus, and rRNA is transcribed in the nucleolus.
What is the nucleolus?
A 1-3µm diameter dense area within the nucleus
What two forms of DNA does the nucleus contain, and what is the difference?
- Euchromatin (DNA that is more dispersed and is actively undergoing transcription).
- Heterochromatin (DNA that is highly condensed and not undergoing transcription).
What is the nucleus surrounded by?
Double nuclear membrane
Where are ribosomes formed, and what are they instrumental for?
Ribosomes are formed in the nucleolus and are instrumental in protein synthesis.
What is each ribosome made of?
A small subunit - which binds RNA, and a large subunit which catalyzes the formation of peptide bonds.
What does the export of ribosomes depend on?
Nuclear pore complex
What does reticulum mean?
Net-like structure
What does the endoplasmic reticulum form?
The endoplasmic reticulum (ER) forms a network of interconnecting membrane-bound compartments in the cell.
What are the two kinds of Endoplasmic reticulum?
- Rough endoplasmic reticulum
- Smooth endoplasmic reticulum
Why is it called Rough Endoplasmic Reticulum?
Because it is studded with ribosomes
What is the role of the Rough Endoplasmic Reticulum?
It plays a vital role in synthesizing proteins destined for insertion into membranes or secretion.
What does the amount of ER present depend on?
It varies with how active the cell is. Cells that are relatively metabolically inactive have relatively little ER.
What is the rough endoplasmic reticulum associated with, and what does it initiate?
The rough endoplasmic reticulum is associated with protein synthesis and the initiation of glycoprotein formation.
What is the function of the smooth endoplasmic reticulum, and what vital role does it play?
The SER continues the processing of proteins produced in the RER.
The SER plays a vital role as the site of the synthesis of lipids.
Most cells contain relatively little SER, but in what cells is it extensive?
Cells synthesizing steroid hormones
What is the Golgi apparatus?
The Golgi apparatus (complex) comprises a group of flattened, membrane-bound cisternae. These are arranged in
sub-compartments.
What is the function of Golgi cisterns?
Golgi cisterns function in the modification and packaging of macromolecules that were synthesized in the ER. Transport vesicles arrive at the Golgi from the SER/RER.
What three things do the Golgi cisterns add to macromolecules from ER?
Adds sugars
Cleaves some proteins
Sorts macromolecules into vesicles.
What are mitochondria, their size, and their function?
-Mitochondria are oblong, cylindrical organelles, typically 0.5-2µm in length.
-Mitochondria are the power generators of the cell. They function in the generation of ATP via oxidative phosphorylation and in the synthesis of certain lipids and proteins
What are mitochondria composed of?
They are composed of an outer and an inner membrane. The inner membrane is extensively folded to form cristae, which act to increase the available surface area.
What are intercellular junctions, and where are they prominent?
Intercellular junctions are specialized membrane structures that link individual cells into functional units.
They are exceptionally prominent in epithelia.
What are the three types of junctions and their functions?
-Occluding junctions: link cells to form a diffusion barrier.
-Anchoring junctions: provide mechanical strength.
-Communicating junctions: allow movement of molecules between cells.
What do occluding junctions prevent and appear as?
They prevent diffusion.
They appear as a focal region of close apposition between adjacent cell membranes.
What are occluding junctions also known as?
Tight junctions or zonula occludens
What are anchoring junctions also known as?
Adherent junctions
Zonula adherens
What is the structural function of adherent junctions?
Link submembrane actin bundles of adjacent cells
How does each cell bind to the other?
Transmembrane cadherin molecules bind to each other in the extracellular space and to actin of the cytoskeleton.
What are desmosomes, what do they do, what are they known as and where are they very commonly found?
They are adhesive proteins.
They link submembrane intermediate filaments of adjacent cells.
Also called Macula Adherens.
Very common in skin where they provide mechanical stability.
What do Communicating junctions allow and what are they also termed?
Selective diffusion of molecules between adjacent cells. Often termed gap junctions.
What are the structures of the communicating junctions like?
Each junction is studded with several hundred pores.
What proteins produce the pores?
Connexon proteins
Where are communicating junctions found?
Found in epithelia, but also in some smooth muscles and in cardiac muscle, where it is critical for the spread of excitation.
What is a junctional complex?
The close association of several types of junctions found in certain epithelia tissues
What are three ways in which material endocytoses and exocytoses?
Diffusion
Via transport proteins (Pumps or channels)
By incorporation into vesicles (Vesicular transport)
What happens in endocytosis and what is it mediated by?
The cell membrane invaginates, fuses, and the newly made endocytotic vesicle (Endosome) buds into the cell. This process is often receptor-mediated.
What is the cell cycle and how long does it last?
The cell cycle is the period of time between the birth of a cell and its own division to produce two daughter cells.
-It lasts for at least 12 hours, but in majority of adult tissues, it lasts much longer.
Define in-vitro
Performed or taking place in a test tube, culture dish, or elsewhere outside a living organism.
What are cells that continue to divide regularly into definite intervals described as?
Cycling cells
What are the two basic parts the cell cycle is divided into?
-Mitosis (M) phase.
-Interphase, which is divided into G1 phase, S phase, and G2 phase.
What is interphase?
The interval between the end of mitosis and the beginning of the next. The cell is either resting or performing its function.
What is the S phase, when does it start and when does it finish?
The period in which DNA is synthesized, for there to be sufficient for two daughter cells.
-Begins 8 hours after the end of mitosis and takes about 7 to 8 hours to complete.
What is the G1 phase?
The gap in the cell between the end of mitosis and the beginning of the S phase.
What happens in the G1 phase?
This is the period when cells respond to growth factors directing the cell to initiate another cycle. It is also the phase in which most of the molecular machinery required to complete another cell cycle is generated.
Is the G1 phase where growth factors are involved reversible?
Nope, irreversible
How long is the G1 phase?
G1 shows considerable variation, sometimes ranging from less than 2 hours in rapidly dividing cells, to more than 100 hours within the same tissue.
What is the G0 Phase and what do cells are called when they enter it?
Cells retain the capacity for proliferation and are in the process of differentiation but are no longer dividing. They are referred to as QUIESCENT and do not enter S phase.
What can stimulate quiescent cells to leave G0 and enter the cell cycle?
Growth factors
What can stimulate quiescent cells to leave G0 and enter the cell cycle?
Growth factors
What molecules block the cycle in G1?
Proteins encoded by certain tumor suppressor genes (The gene mutated in retinoblastoma, Rb)
What is the G2 Phase and how long does it last?
The gap between the end of the S phase and the beginning of mitosis is the G2 phase. Takes 2 to 4 hours to complete.
What occurs in G2?
During G2, the cell prepares for division; this period ends with the breakdown of the nuclear membrane and the onset of chromosome condensation.
What are the four nuclear changes that achieve this distribution of cells?
-Prophase
-Metaphase
-Anaphase
-Telophase
What four things occur in Prophase?
- The individual chromosome is first visualized as thin threads and is tightly coiled along the entire length
- Each chromosome splits longitudinally into two chromatids except at the centromere.
- The two paired centrioles are separated from each other by the elongation of continuous microtubules of the achromatic spindle and occupy the opposite pole of the nucleus.
- Subsequently, the nuclear membrane and nucleolus disappear.
What happens in prometaphase?
The chromosomes are now entangled in a meshwork of continuous microtubules.
How long does the prophase take to complete?
1.5 hours
What three things happen in metaphase and how long does it take?
- Centromere region from each chromosome presents a bilateral disc (Kinetochores)
- From kinetochores, a set of chromosomal microtubules are organized and extend bilaterally towards opposite centrioles.
- The growth of the chromosomal microtubules allows the centromere of individual chromosomes with their paired chromatids to occupy the equatorial plane of the spindle.
-Persists for 20 minutes.
What is Colchicine?
A medicine for treating inflammation and pain.
What three things does Colchicine do and what is it so important?
-It arrests the cell division at metaphase.
-Prevents the formation of microtubules of the spindle
-In colchicine-treated metaphase, the chromosomes are found to assemble around centriole
-Application of colchicine in cell culture is an important tool in karyotyping
What happens in Anaphase?
- The centromere split longitudinally and chromatids separate to form two new chromosomes.
- The spindle fibers contract and each pair of newly formed chromosomes separate and migrates to the opposite pole of the spindle. Two identical and complete chromosomes are formed.
- The separation of the chromatids to form new chromosomes occurs by contraction of chromosomal microtubules which exert a centrifugal force in the centromere region.
How long does Anaphase take?
2-3 minutes
What two things can go wrong in Anaphase? Describe them.
-Non-disjunction: Due to abnormal function of the spindle apparatus one or more chromosomes fail to migrate properly in anaphase. Leading a daughter cell to receive extra chromosomes and another daughter cell is deficient in this chromosome.
-Isochromosome: Sometimes, the centromere splits transversely instead of longitudinal division. This leads to the formation of two daughter chromosomes of unequal length.
What five things happen in Telophase?
- The daughter chromosomes are enveloped by a new nuclear membrane and nucleolus appears.
- The chromosomes become uncoiled and their individual identity is lost.
- The cytoplasm divides and two complete cells are formed.
- In the process of cytokinesis, the cleavage furrow develops around the equator region of the achromatic spindle.
- The contraction of the fibrillar component of the cytoplasm help in hour glass constriction of cleavage.
What is Telophase described as?
A reorganization period.
How long does the telophase last?
Telophase 3 to 12 minutes and the reconstruction period from 30 to 120 minutes
What is the organizational structure in histology?
Cell
Tissue
Organs
Organ System
Organism
What are the three histological techniques?
-Tissue Processing
-Embedding and sectioning
-Staining
Draw the process of tissue processing.
Check-in histology notion
What do embedding and sectioning involve?
Slicing the desired section and putting it in the glass to view under the microscope
What are the three kinds of stains?
Acidic Stains
Basic Stains
Neutral Stains
What are the two most common stains, and how do they work?
-Hematoxylin (basic dye) binds to DNA / RNA and colors the nucleus blue/purple
-Eosin (acidic dye) binds to amino acids/ proteins, thus colors cytoplasm pink
What is an example of an acidic stain what does it mean if tissue components stain?
Eosin is an acidic stain that goes red/pink.
Tissue components which take this type of stain are ACIDIC
What is an example of an acidic stain what does it mean if tissue components stain?
Eosin is an acidic stain that goes red/pink.
Tissue components which take this type of stain are ACIDIC
What is an example of an acidic stain what does it mean if tissue components stain?
Eosin is an acidic stain that goes red/pink.
Tissue components which take this type of stain are ACIDIC
What are two examples of a basic stain and what does it mean if tissue components stain?
Hematoxylin and toluidine blue.
Tissue components which take this type of staining are BASOPHILIC
What happens with neutral stains?
Give different color to different components.
What are the four basic tissue types?
Epithelium
Connective Tissue
Muscle Tissue
Nervous Tissue
What are the four basic tissue types?
Epithelium
Connective Tissue
Muscle Tissue
Nervous Tissue
What three things do the epithelia do?
-Cover surfaces of the body
-Line hollow organs
-Form glands
What is the structure of the epithelia?
Occur as sheets of cells and vary widely in size, shape, orientation & function.
What is the function of connective tissue, and what is its dynamic role?
-Forms the framework of the body
-Also has a dynamic role in the development, growth, and homeostasis of tissues and, via fat, in energy storage.
What is the muscle tissue specialized to do and what are the three major types?
-Specialized in contracting and generating force by contracting.
-Three major types
Cardiac
Skeletal
Smooth
What is the nervous tissue specialized to do and what does it consist of?
-Specialized in conducting impulses.
-Consists of neurons and supporting cells.
What is the nervous tissue specialized to do and what does it consist of?
-Specialized in conducting impulses.
-Consists of neurons and supporting cells.
What are the three characteristics of epithelia?
-Polarity: Apical and basal.
-Tightly adherent: Cell junctions and cytoskeleton.
-Avascular.
Draw the classification of epithelia.
Check-in notion– Histology
What are the four ways to classify surface epithelia?
1.Number of layers of cells
2.Cell shape
3.Cell surface, or tissue surface, specializations
4.Presence of any specialized cell types
What are the three layers and their names?
Simple: One layer
Stratified: Several layers
Pseudostratified: Appears stratified but all cells contact basal lamina
What are the three cell shapes?
- Squamous (Flat plate-like)
- Cuboidal (Height similar to width)
- Columnar (Height 2-5 times width)
What are the three cell shapes?
- Squamous (Flat plate-like)
- Cuboidal (Height similar to width)
- Columnar (Height 2-5 times width)
What are the three surface specializations?
-Cilia
-Keratin
-Microvilli
What are microvilli, where are they present, and what is the example?
The microvilli are minute finger-like projections at the apical end of the cells,
They are present in the absorptive epithelia and increase the cells’ surface area.
Such as in the small intestinal epithelium, where these microvilli give an appearance of a brush border.
What are the two divisions of epithelium?
Surface and Glandular
What are the two divisions of glandular epithelium, and what are they also called and why?
-Exocrine: Also called as ducted glands, they secrete their products onto a surface directly through a duct.
-Endocrine: Also called ductless glands because they lack a duct system and secrete their products into the bloodstream, and their products, called hormones, are distributed by the vascular system.
What are the two examples between exocrine and endocrine glands?
-Salivary gland (Exocrine)
Ducts present with secretory acini
-Anterior Pituitary gland (Endocrine)
No ducts lot of capillaries
Draw the classification of Connective Tissue.
Check-in notion
What are the four connective tissue components in cells?
*Fibroblasts: widely distributed cells that produce and maintain the extracellular matrix.
*Adipose cells: fat cells found scattered in many connective tissues, but a predominant cell in adipose tissue (fat)
*Osteocytes: cells of bone
*Chondrocytes: cells of cartilage
What is the Extracellular Matrix?
An extensive network of proteins and other molecules surround, support, and give structure to cells and tissues in the body.
What three connective tissue components are in the Extracellular Matrix?
*Fibres: collagen, reticular and elastic fibers
*Ground substance: an amorphous, space-occupying material made of giant unbranched polysaccharide molecules called glycosaminoglycans (GAGs), most of which are bound to protein cores to form glycoproteins
*Tissue fluid
What are the two divisions of Dense Connective Tissue, and how do you know which one is which?
These are densely packed bundles of collagen fibers.
-Dense regular C.T. - if the fibers are aligned (e.g., tendon).
-Dense irregular C.T.- if the fiber bundles run in many directions (e.g., the skin’s dermis).
What is cartilage? Where does the semi-rigid nature of the matrix come from?
Strong, flexible, compressible, semi-rigid tissue.
The semi-rigid nature of the matrix comes from the highly hydrated nature of the ground substance (GAGs and proteoglycans).
Where does the cartilage receive the nutrients from?
As they are avascular, it receives nutrients from adjacent tissues by diffusion through their matrix.
What are the three types of cartilage?
Hyaline
Elastic
Fibrous
What is the most common type of cartilage?
Hyaline Cartilage
What is the Hyaline Cartilage?
A translucent bluish-white type of cartilage is present in the joints, the respiratory tract, and the immature skeleton.
What is the Fibrocartilage?
They are collagen fibers bundles in the extracellular matrix, single chondrocytes in lacunae.
What is elastic cartilage?
Thin Elastic fibers with ground substance in the extracellular matrix, groups of chondrocytes in lacunae.
Is the bone a living tissue and undergoes remodeling throughout life?
Yessir
What are Osteons?
Osteons are cylindrical vascular tunnels formed by osteoclast-rich tissue.
What are Haversian canals?
Haversian canals are a series of microscopic tubes in the outermost region of bone called cortical bone that allows blood vessels and nerves to travel through them.
What is muscle specialized for? What are their two contractile fibers? And what are the three main types of muscle?
-Specialized in contraction
-Actin and Myosin
-Types
Cardiac
Skeletal
Smooth
How is the contractile force produced?
Force is produced by the movement of actin fibers over myosin fibers, with the aid of a number of accessory proteins.
What do smooth muscle cells look like and their size?
Elongated, spindle-shaped cells
Length range 20 -200 µm
What do the smooth muscle cell’s nuclei look like?
Central cigar-shaped nucleus
What are two sections in which smooth muscle can be viewed?
-Longitudinal section
The section along the long axis of the fibre
Spindle shape with a central nucleus
-Transverse section
Section across the fibre
Rounded section of fibres with a central nucleus
What are the three characteristics viewed in cardiac muscle? Is it a voluntary or involuntary movement?
Striated
Short, Branched fibers (Length range 50-100µm)
Intercalated Disc
Involuntary
What are the four characteristics viewed in skeletal muscle? Is it a voluntary or involuntary movement?
Striated
Long & Unbranched (Length range 1-40 mm / Diameter 10-100µm)
Multinucleated Cells
Peripheral Nuclei
Voluntary
What are the two characteristics viewed in smooth muscle? Is it voluntary or involuntary?
No Visible striations
Involuntary / Visceral
What are intercalated discs, what two junctions are present, and what are their function?
Sites of end-to-end attachments between branching cells
Intercellular junctions – maintain the integrity
Gap junctions – Ensure synchronous contraction
Draw and label a neuron
Check Google
What is the connective tissue coat for both Nervous systems?
Meninges (CNS)
Perineurium (PNS)
What are the three types of neurons regarding structure? And describe each one.
-Multipolar Neuron
Multiple Dendrites
One Axon
-Multipolar Neuron
Multiple Dendrites
One Axon
-Pseudo-unipolar Neuron
One cytoplasmic process (Axon)
Central process
Peripheral process
What are three Glial cells?
Microglia: provide immune surveillance
Astrocytes: support, ion transport, form blood-brain barrier
Oligodendrocytes: produce myelin in the brain & spinal cord
Neuro-lemmocyte / Schwann Cell: Produce myelin and Support axons
Difference between Schwann cells and oligodendrocytes?
The difference between Schwann cells and oligodendrocytes lies in the type of nerve cell axons they insulate. Schwann cells insulate the axons of the nerve cells in the PNS whereas oligodendrocytes insulate the nerve cells in the CNS
What are the four basic layers in the Gastro-Intestinal Tract?
- Mucosa
- Submucosa
- Muscularis
- Serosa/ Adventitia
What are the three layers of the mucosa?
Epithelium
Lamina propria
Muscularis Mucosa
What are the two layers of muscularis?
Muscularis Externa (Longitudinal) - Nerve plexus
Muscularis interna (Circular)
What are the four variations in the mucosa of the Gastrointestinal tract?
Protective
Absorptive
Secretory
Protective and absorptive
What are the protective mucosa variation and where can we find them?
Protective: Non-keratinized stratified squamous epithelium.
Oral cavity, pharynx, esophagus, and anal canal.
What are the absorptive mucosa variation and where can we find them?
Absorptive: simple columnar epithelium with villi & tubular glands.
Small intestine
What are the secretory mucosa variation and where can we find them?
Simple columnar epithelium with extensive tubular glands.
Stomach
What are the protective and absorptive mucosa variations and where can we find them?
Simple columnar epithelium with tubular glands.
Large intestine
What are the four associated organs in the digestive system?
- Salivary glands
- Liver
- Gall Bladder
- Pancreas
What are the three salivary glands?
Parotid
Submandibular
Sublingual
What salivary glands have serous secreting cells?
All three (Parotid, submandibular and sublingual)
What salivary glands have mucous-secreting cells?
Submandibular and sublingual
What salivary glands have striated ducts?
Parotid and submandibular
What are the four lobes of the liver?
Anatomically the liver has four lobes: right, left, caudate, and quadrate.
What is the portal triad?
The hepatic artery proper, common bile duct, and portal vein run through the ligament near its free edge to reach the liver.
What is the dynamic between the portal triad and the central vein?
Blood flows from the portal and hepatic artery towards the Central vein through sinusoids (Small blood vessels between the radiating rows of hepatocytes)
What shape are the hepatic lobules?
Roughly hexagonal hepatic lobule
What are the pancreas and its two portions?
-Mixed gland
-Exocrine Portion
Serous acini
Produce digestive juices, proteases, lipases
-Endocrine Portion
Islet of Langerhans
Produce insulin, glucagon
What are the four main parts of the respiratory system?
Upper respiratory tract
Trachea
Bronchial Tree
Lungs
What are the three layers in the trachea?
-Respiratory epithelium
-Lamina Propria
-Hyaline cartilage of tracheal ring
What are the characteristics of respiratory epithelium and what does it have?
Pseudo-stratified, ciliated columnar epithelium with goblet cells
Regarding the bronchi, what is the diameter like, and do they have cartilage?
Large diameter airways
Have hyaline cartilage in their wall
Regarding the bronchi, what is the diameter like, and do they have cartilage?
Smaller airways
Have no cartilage in their wall
Smooth muscle predominates in their wall
What happens to columnar cells of the epithelium as you go down the respiratory tree?
Columnar cells of epithelium get shorter as we go down the respiratory tree
What are alveoli lined by?
They are lined by simple squamous epithelium
What are the two parts and the main functional unit of the kidney?
-Cortex.
-Medulla.
-The main functional unit is the Nephron.
What two things can be found in the medulla?
Loop of Henle, thick and thin segment
Collecting duct (CD)
What three things can be found in the kidney cortex?
Renal corpuscle (glomerulus & bowman’s capsule)
Proximal Convoluted tubule (PCT)
Distal Convoluted tubule (DCT)
What are the three layers of blood vessels and what composes each one?
-Tunica intima
Endothelium
Subendothelial C.T
-Tunica media
Smooth Muscles
-Tunica externa
Connective Tissue
Describe the structure of the tunica intima.
Tunica intima, a single layer of squamous epithelial cells termed endothelial cells supported by a basal lamina and a thin layer of connective tissue.
Describe the structure of the tunica media.
Tunica media is made up predominately of smooth muscle. The thickness of this layer varies tremendously.
Describe the structure of the tunica adventitia.
Tunica adventitia is made up of supporting connective tissue.
What separates the tunica media from the tunica media?
By a layer of elastic tissue called the internal elastic membrane.
What separates the tunica media from the tunica adventitia?
By a layer of elastic tissue called the external elastic membrane.
What are elastic fibers stained with instead of H&E, and what color is turned for elastic fibers, collagen, and smooth muscle?
Verhoeff’s/Masson trichrome stain: elastic fibers black, collagen green, and smooth muscle cells red
What are elastic arteries?
In the largest arteries (e.g. aorta) a significant amount of the smooth muscle in the tunica media is replaced by sheets of elastic fibers to provide elastic recoil.
What are the vasa vasorum and its function?
Means the Vessel of the vessels, found in tunica media. The function of vasa vasorum is both to deliver nutrients and oxygen to arterial and venous walls and to remove “waste” products.
What are the structure of the arteriole and its size?
Arterioles have only one or two layers of smooth muscle in their tunica media and almost no adventitia. Typical diameter: 30- 200µm.
What are arterioles important for?
These are particularly important in controlling blood flow in tissue.
What are the structure of capillaries and their size?
Capillaries are essentially composed of endothelial cells and a basal lamina.
They have a diameter of 4- 8µm.
What are the three types of capillaries, what do they look like and where can we find them?
-Continuous: muscle, nerve, lung, skin
-Fenestrated: have small pores (50nm), gut mucosa, endocrine glands, kidney
-Discontinuous or Sinusoidal: have large gaps, liver, spleen, bone marrow
What is the microvasculature from arterioles to precapillary sphincters?
Small arteriole connected to a postcapillary venule (PCV) through a network made up of metarterioles (MT), thoroughfare channels (TC), and capillaries (C). Precapillary sphincters (PS), composed of smooth muscle, at the beginning of the capillary help control flow through the network.
What do capillary networks drain into?
Post-capillary venules.
What are post-capillary venules, their size, and what are they important for?
Endothelial cell-lined and contain a thin layer of connective tissue.
These are important sites for exchange, e.g, cells moving into the tissue in inflammation.
When are vessels referred to as venules?
Once the vessel begins to acquire intermittent smooth muscle in a tunica media layer (Generally >50µm)
What are the structures of veins?
A tunica intima, is a thin but continuous tunica media, typically consisting of a few layers of smooth muscle cells. Plus, there is an obvious tunica adventitia.
What do large veins (e.g Vena Cava) have structurally?
A thick tunica adventitia that incorporates bundles of longitudinaly oriented smooth muscle.
What do small veins have to prevent a backflow of blood?
Valves, which are an inward extension of the tunica intima.
What is the function of the Lymph Vascular System and what do its vessels look like structurally?
This system drains excess tissue fluid (Lymph) into the bloodstream and transports lymph to lymph nodes for immunological surveillance.
Thin-walled vessels
What elements produce flow in the lymphatic system?
Smooth muscle in walls, hydrostatic pressure in the tissue, and compression of the vessels by voluntary muscle, combined with valves in the vessels.
Where can most blood be found in the body?
In the peripheral arteries
What is the average adult blood volume?
4.5-6 litres
What are the blood components?
Formed elements (45%)
Plasma (55%)
What three things are plasma composed of?
Water (~90%)
Proteins (Mostly albumin, immunoglobins, and clotting factors)
Nutrients and Salts
How can you separate blood?
By spinning in a centrifuge
What is the distribution after spinning the blood in a centrifuge?
-The red cells are densest and after spinning are found at the bottom of the tube.
-The white cells are next
-Plasma which is the liquid portion of blood, is found on top.
What is the liquid termed if the clotting factors are first removed from the blood?
Serum
How is serum usually obtained?
By allowing the blood to clot, and then removing the clot before spinning the blood.
What are erythrocytes?
These are biconcave discs of about 7µm in diameter.
Why are mature erythrocytes called not true cells? And what protein do they carry?
As they have no nucleus or organelles. They are basically deformable bags with 1/3 of their volume taken up by the iron-containing protein hemoglobin
What is their cytoskeleton like?
They contain a network of flexible cytoskeletal elements that allow them to deform and slip through spaces smaller than themselves.
How long do erythrocytes remain in circulation and what removes them?
They last approximately 4 months and aged cells are removed by the spleen and liver.
What are the five leukocytes?
- Neutrophils
- Eosinophils
- Basophils
- Lymphocytes
- Monocytes
What is the most common type of leukocyte?
Neutrophil
Describe the life span of a neutrophil.
Abundant and short-lived which means that a significant portion of the bone marrow is devoted to their production.
What form do neutrophils circulate?
Inactive state
What kind of cells are neutrophils, why are they called that way and what is their cytoplasm & nuclei like?
They are granulocytes.
Their cytoplasm contains many granules but these stains poorly with either acidic or basic dyes, hence the name neutro.
They have prominent and multilobed nucleus.
What kind of cells are neutrophils, why are they called that way and what is their cytoplasm & nuclei like?
They are granulocytes.
Their cytoplasm contains many granules but these stains poorly with either acidic or basic dyes, hence the name neutro.
They have prominent and multilobed nucleus.
What are eosinophils, their functions, and what are they important for?
Eosinophils typically have a bilobed nucleus. Their granules contain a variety of hydrolytic enzymes and they are important in inducing and maintaining inflammation, particularly in allergic reactions and asthma. They are also important in fighting parasitic infections.
What are eosinophils stained with?
The prominent granules in the cytoplasm of eosinophils have an affinity for the red acidic dye eosin.
Where are eosinophils developed and released? For how long do they circulate?
These cells are released from the marrow and circulate for 8-12 hours and then move into the tissue (particularly the spleen, lymph nodes, and GI tract) where most eosinophils live.
Which are larger: Neutrophils or Eosinophils?
Eosinophils are slightly larger than neutrophils
What are the rarest granulocytes?
Basophils
What are basophils stained with?
The prominent granules in their cytoplasm have an affinity for basic dyes such as methylene blue and with this dye, stain intensely blue-purple.
What is the basophil’s nucleus like and what three things do its granules contain?
The cells have a bilobed nucleus but this is often obscured by the granules. These granules contain histamine, heparin, and other inflammatory mediators
How do basophils work and what reactions/diseases can they cause?
Basophils act as effector cells in allergic reactions. High-affinity IgE receptors in their cell membrane are directed against a particular allergen and when they bind their antigen the cell is stimulated to release its granules (termed degranulation). This leads to hayfever, allergic asthma, allergic dermatitis, etc.
What are the precursors of tissue macrophages?
Monocytes
What do monocytes and macrophages form?
They form what is termed the mononuclear phagocyte system.
Where are macrophages found?
Macrophages are widely distributed in the body, but are particularly found in loose connective tissue
What are the largest cells in circulation?
Monocytes
What are the nuclei and cytoplasm of monocytes like?
Monocytes have numerous small lysosomal granules in their cytoplasm. Have a non-lobulated nucleus which often appears kidney bean-shaped.
Where can wanderers of the mononuclear phagocytic system end up? (Three examples)
Kupffer cells in the liver, microglia in the brain, and Langerhan’s cells in the skin.
What do lymphocytes look like regarding nuclei and cytoplasm?
Lymphocytes have a round nucleus surrounded by a thin to the moderate rim of cytoplasm that does not have visible granules.
What are the two types of lymphocytes and how can they be stained?
There are two general classes of lymphocytes, B cells, and T cells, however, these cannot be distinguished in routinely stained sections.
What are platelets, their size, and what is their role?
These are small cell fragments about 2µm in diameter found in large numbers in the blood.
Platelets play a key role in hemostasis (the prevention of blood loss).
What is the cytoskeleton for platelets like and what does it participate in?
Platelets have a well-developed cytoskeleton, which participates in the extrusion of granules and in clot retraction.
Platelets have no organelles and no nucleus. True or False?
FAUUUUUUUUUUUUUUUUUUUUUUX
Platelets have some organelles, but no nucleus.
What do platelets contain in their cytoplasm?
They have conspicuous granules that include, among other things, some coagulation factors.
What is hemopoiesis and where does it occur?
The production of blood cells and platelets, occurs in the bone marrow.
When and where is the earliest site for erythrocyte formation?
The earliest site for erythrocyte formation is outside the embryo in the yolk sac beginning at about 3 weeks gestation.
What occurs later in a fetal liver and spleen?
Later, the liver and to some extent the spleen are colonized by hemopoietic stem cells. Thus during the second trimester, the liver is the principal site of blood formation.
What five bones retain hematopoiesis?
By the time the skeleton reaches maturity, only the vertebrae, ribs, skull, pelvis and proximal femurs retain hemopoiesis
What can be done in an emergency involving blood with bone marrow?
Marrow in other bones is largely adipose tissue, although in an emergency, they can revert to blood formation
What are megakaryotes? Their sizes, their function, what their nuclei look like, and what does it undergo?
Megakaryocytes are large (30- 100µm) cells of bone marrow that produce platelets. It undergoes multiple duplications of its nuclear material but doesn’t undergo nuclear or cell division – so the nucleus is very large. The platelets are formed as extensions at the outer margin of the cell which fragment from the cell
