IMMS Flashcards
What colour do nerve cells stain?
Shades of brown
What cells are in the spinal cord?
Within the spinal cord are some motor neurons. These are some of the largest cells in the body (see image below).
What do motor neurones show?
Motor neurons in the ventral horn of the spinal cord showing axons or dendrites arising from them. These are described as multipolar cells because when seen whole they have more than two processes.
What are lymphocytes like?
- among the smallest nucleated cells in the body
- circulate in the blood and are found in large numbers in organs such as in lymph nodes, the tonsils and the thymus gland
- Many tissues also have lymph nodules full of lymphocytes within their fabric.
What can the lymph node be stained with?
Part of a lymph node stained with H&E showing many small lymphocytes.
What does the nucleus of lymph nodes stain?
The nuclei of these cells stain dark blue but their cytoplasm is very scanty
Which dyes are used to stain?
two dyes, haematoxylin and eosin. This is often referred to as H&E staining.
What colour does H&E stain?
Haematoxylin stains cell nuclei blue and eosin stains cell cytoplasm and many extracellular fibres pink.
What does the dark blue stain of a cell nucleus show?
The cell nucleus that stains dark blue with haematoxylin can tell you a lot about the metabolic activity of a cell.
What does the size of the cell nucleus show?
A large cell nucleus often denotes a highly active cell whereas a thin or small nucleus in which it is difficult to see any of the infrastructure often denotes a relatively dormant cell.
What is thyroid histological image like?
Image shows:
• roughly circular structures (in 2D – spheres in 3D)
•Each lined by a single layer of cuboidal/columnar epithelial cells
•Centre of each structure is acellular, filled with a homogenous eosinophilic material
What are tissue slices size?
Thinner than a cell
What is the most common dye?
Haematoxylin and Eosin (H&E).
Many extra cellular fibres e.g. collagen,elastic stain pink
What does not stain?
Watery extra-cellular jelly does not stain at all
What are the other stain?
PAS - sugars
Van Gieson - elastic
Trichromatic - 3 types of cell
Alcian blue - mucins
What are the size of lymphocytes?
Small cells – lymphocytes about 10 micrometres in diameter, with very little cytoplasm
What are the size of motor neurones?
Large cells – motor neurons 100 micrometres wide with axons up to 1 meter in length
What are the shapes of cells?
Rounded
Polygonal
Fusiform
Squamous (flattened)
Cuboidal
Columnar
How does metabolic activity relate to size of cell?
Inactive/dormant cells are smaller
Metabolically active cells often have nucleoli
What cells last days, months, years?
Days: lining of the gut
Months: lots of tissues –
blood
skin
connective tissues
Years: bone and tendons
Nearly whole life: (limited regeneration) skeletal muscle
Whole life: nerves and brain
cardiac (heart) muscle
germ cells
What does the nucleus contain?
Euchromatin
Heterochromatin
Nucleolus
Double nuclear membrane
DNA
What occurs at the nucleolus?
1-3 microns in diameter
Site of ribosomal RNA formation
What is the mitochondria like?
Powerhouses of the cell
Site of oxidative phosphorylation
Have their own DNA
Double membrane – inner membrane is
What occurs at the outer and inner membrane of the mitochondria?
Outer:Lipid synthesis
FA metabolism
Inner: Respiratory chain
ATP production
What occurs in the matrix and intramembranous space of the mitochondria?
Matrix - TCA (Krebs’) cycle
Intermembranous space - Nucleotide phosphorylation (ADP to ATP)
What occurs in the matrix and intramembranous space of the mitochondria?
Matrix - TCA (Krebs’) cycle
Intermembranous space - Nucleotide phosphorylation (ADP to ATP)
What occurs at the RER?
Site of protein synthesis
Highly folded flattened membrane sheets
What occurs at the SER?
Site of membrane lipid synthesis
Processes synthesised proteins
Highly folded flattened membrane sheets
What occurs at the Golgi apparatus?
Parallel stacks of membrane
Processes macromolecules synthesised in the ER
Particularly prominent in Plasma cells – seen as a perinuclear ‘hoff’
What are the faces of the Golgi apparatus?
Cis face
- nuclear-facing receives transport vesicles from SER phosphorylates some proteins
Trans Golgi network
Proteolysis
Sorts macromolecules into vesicles which bud from the surface
Medial Golgi
Central part
Forms complex oligosaccharides by adding sugars to lipid and peptides
What are vesicles?
Very small spherical membrane-bound organelles used for transport, storage and exchanging cell membrane between compartments
What are the types of vesicles?
Several types:
Cell-surface derived pinocytotic and phagocytotic vesicles
Golgi-derived transport vesicles
ER-derived transport vesicles
Lysosomes
Peroxisomes
What are lysosomes like?
Derived from Golgi apparatus
H+-ATPase on membrane creates low internal pH (pH 5)
Contain acid hydrolases that degrade proteins
Initial hydrolase vesicles fuse with endosomes with the correct membrane proteins to produce endolysosomes
What are perioxosomes like?
Small (0.5-1.0 microns) membrane-bound organelles containing enzymes which oxidise long-chain fatty acids
What is the cytoskeleton composed of?
Plasma membrane
Microfilaments
Mitochondrion
Intermediate filaments
Endoplasmic reticulum
Microtubule
Vesicle
What are the microfilaments like in the cytoskeleton?
Microfilaments - 5nm diameter ACTIN
Globular G-actin polymerises into filamentous F-actin
Forms a bracing mesh (cell cortex) on the inner surface of the cell membrane
What are the micro tubules in the cytoskeleton like?
Microtubules - 25nm diameter TUBULIN proteins
All cells except erythrocytes
Made of α- and β-tubulin which arrange in groups of 13 to form hollow tubes
What are the micro tubules in the cytoskeleton like?
Microtubules - 25nm diameter TUBULIN proteins
All cells except erythrocytes
Made of α- and β-tubulin which arrange in groups of 13 to form hollow tubes
What is the intermediate filaments in the cytoskeleton like?
Intermediate filaments - 10nm diameter - 6 types of protein
- Anchored to transmembrane proteins
- Spread tensile forces through tissues
- Specific functions generally not known
- Useful to tell one cell type from another
What are the localisation of intermediate filaments in the cytoskeleton?
Cytokeratins - Epithelial cells
Desmin - Myocytes
Glial fibrillary acidic protein - Astrocytic glial cells
Neurofilament protein - Neurons
Nuclear laminin - Nuclei of all cells
Vimentin - Mesodermal cells
What are the localisation of intermediate filaments in the cytoskeleton?
Cytokeratins - Epithelial cells
Desmin - Myocytes
Glial fibrillary acidic protein - Astrocytic glial cells
Neurofilament protein - Neurons
Nuclear laminin - Nuclei of all cells
Vimentin - Mesodermal cells
What are lipofuscin?
Lipofuscin
Membrane-bound orange-brown pigment
Peroxidation of lipids in older cells
Common in heart and liver
What are lipids and glycogen like?
Lipid
Non-membrane-bound vacuoles
Appear as empty space as dissolve in processing
Adipocytes and liver
Glycogen
CHO polymer in cytoplasm
Normally only seen on electron microscopy
Accumulates in some cells & diseases
What is the composition of tissues?
Cells
Interstitial fluid
water
salts in solution
peptides and proteins (e.g. plasma proteins, hormones, etc.)
Extracellular material
Fibrillary proteins – e.g. tendons
Glycosaminoglycan jelly
inorganic salts as solids
What are the types of tissue?
Epithelia - protection, absorption, secretion
Muscle - smooth, skeletal, heart
Supporting tissues - cartilage, bone, tendons, blood
Nerves - brain, peripheral, visceral
Germ cells - ova, sperm
What are epithelia?
Epithelia comprise a cohesive sheet of cells, with one or more layers, resting on a basement membrane.
What are epithelia found?
Form barriers for:
Protection – e.g. skin
Absorption – e.g. gut
Secretion – e.g. pancreas
How are epithelia categorised?
Categorised according to the shape of the cells and the number of layers of cells.
What is simple epithelia and stratified (compound) epithelia?
Simple epithelia
Single layer of cells on a
basement membrane
Stratified (compound) epithelia
Two or more layers of cells on
a basement membrane
What is simple squamous epithelium?
- Single layer of flattened plate-like cells on a basement membrane
- Parallel oval nuclei (1 per cell)
Where is simple squamous epithelium found?
Lines inside of blood vessels (endothelium), outside of lungs (mesothelium) and abdominal organs (peritoneum)
E.g. lung alveoli
What is simple cuboidal epithelium?
- Single layer of cells with similar height and width on a basement membrane
- Central spherical nuclei (1 per cell)
Where is simple cuboidal epithelium found?
- Line kidney tubules, small ducts
E.g. salivary glands and kidney
What are simple columnar epithelium?
Single layer of cells taller than they are wide, on a basement membrane
Line the stomach, intestines and uterus
May or may not have cilia or microvilli
Where is simple columnar epithelium found?
Stomach and small intestine
What are mivrovilli?
Microscopic projections on luminal surface of absorptive cells
- Increase surface area
- Intestinal brush border
E.g. small intestine
What are cilia?
Microscopic motile projections on luminal surface of cells
Respiratory tract
Reproductive tract e.g. trachea, fallopian tube
What are stratified epithelia? Where are they?
Features
Protective function
Many layers of cells
Continually being worn down, worn-away cells replaced from below
Locations
Found at sites subject to abrasive forces e.g. pigmented skin
What is stratified squamous non-keratinising epithelium?
Multiple layer of cells on a basement membrane
Mature surface layers are plate-like squames
- Lines the mouth, oropharynx, oesophagus, vagina
What is stratified squamous keratinising epithelium?
Multiple layer of cells on a basement membrane
Mature surface layers are plate-like squames
Waterproof layer of keratin
Skin
What is pseudostratified epithelium?
Single layer of cells of variable height, mimicking multiple layers on a basement membrane
All cells in contact with basement membrane
Lines the conducting airways
What is urothelium?
Specialises stratified epithelium
Breaks the rules – looks stratified, probably is stratified, but:
Surface layer of umbrella cells
Cells between …
What is the basement membrane?
Always present – usually cannot see it
Infer presence – difference between epithelium and underlying connective tissue
What is the basement membrane composed of?
Composed of several extra-cellular proteins including Collagen IV and Fibronectin
Essential for the proper functioning and survival of the epithelium
Can be seen if stained with PAS
What are the types epithelial junctions?
Occluding (tight) junctions
Desmosomes (Anchoring/Adherent junctions)
Gap (aka communicating) junctions
What are tight/occluding junctions like?
Band-like fusions between cells that are impervious to most molecules
Prevent diffusion between cells
What are desmosomes (anchoring/adherent) junctions?
Plaques that form physical joins between cells and connect the cytoskeletons of adjacent cells
Spread forces across several cells
What are gap/communicating jucntions?
Electrical junctions that permit the transfer of small molecules
Electrically couple adjacent cells
What do epithelia comprise?
Epithelia comprise one or more layers of cells resting on a basement membrane
When aren’t basement membranes not visible?
Basement membrane not usually visible in H+E stained sections
What do specialised junctions do?
Specialised junctions connect the epithelial cells together.
What is the origin of connective tissue cells?
Mainly derived from undifferentiated
mesenchymal cells
fibroblast
fat cells
most cartilage and bone cells
But also from the haematopoetic stem cell line
What can mesenchymal cells become?
Mesenchymal cell
- adipocyte (white adipose tissue)
- adipocyte (brown adipose tissue)
- osteoblast -> osteocyte
- mast cell
- fibroblast -> fibrocyte
- chondroblast -> chondrocyte
What are the constituents of connective tissues?
Cells:
fibroblasts/cytes
adipose cells
Visible fibres:
collagen
elastic
reticulin
Ground substance (hydrophilic jelly)
Proteoglycans
Glycosaminoglycans (GAGS)
Laminin, fibronectin etc (invisible fibres)
What are the types of connective tissue?
Fibrous - loose, dense
Hard - cartilage, bone
Fatty - white, brown
What is collagen like?
Tropocollagen - triple helix of peptides
Fibroblasts - secrete tropocollagen subunits
Fibres - assembled extra-cellularly
Triple helix of peptides -> overlapping tropocollagen units -> collagen fibril
What are the types of collagen?
More than 20 types :
Type 1 skin
2 cartilage
3 liver bone marrow spleen (reticulin)
4 basement membranes
5 placenta
What are collagen fibres like?
Extracellular Fibres that stain pink with H&E
Variable thickness and length, often run in bundles
Sometime confused for muscle fibres that also stain pink (but are intra-cellular)
What are collagen fibres like?
Extracellular Fibres that stain pink with H&E
Variable thickness and length, often run in bundles
Sometime confused for muscle fibres that also stain pink (but are intra-cellular)
What comprises loose connective tissue?
Comprises:
Widely spaced thin collagen fibres
Fibroblasts/fibrocytes
Unstained ground substance
What comprises dense connective tissue?
Comprises:
Closely spaced thick collagen fibres
Fibroblasts/fibrocytes
Unstained ground substance
May be irregular (top) or regular (bottom)
What is reticulin?
Type III collagen
Fibrillar collagen
Forms a supporting scaffold in many organs
Bone marrow
Liver, Kidney
Lymph node
Spleen
Not visible on H+E – need a silver stain
What is elastin like?
Elastic tissue contains fine fibres and sheets of elastin
Elastin fibres may be branched
Produced by fibroblasts
Stain pink on H+E
Easily confused with smooth muscle cells
What is white adipose (fatty) tissue like?
Large cells with single fat globule in each cell
Usually appear empty (white) in conventional slides as fat is extracted during processing
Don’t confuse it with lung!
What is brown adipose (fatty) tissue like?
Cells with many globules of fat.
Found across shoulders and down back of newborn.
Important in neonatal thermo-regulation
(generate heat on breakdown)
What are the constituents of cartilage?
Cells
–Chondroblasts
–Chondrocytes
•Extracellular matrix
–Glycosaminoglycans
•Hyaluronic acid
–Proteoglycans
•Condroitin sulphate
•Keratan glycan
Extracellular fibres
- collagen
- elastin
Cartilage is avascular
What is hyaline cartilage like?
Found in synovial joints
•Chondrocytes in lacunae surrounded by a glassy amorphous matrix
•No visible fibres
•Perichondrium – fibroblasts and collagen
What is in elastic cartilage?
Found in the pinna, epiglottis
•Visible elastic fibres in matrix
•Perichondrium – fibroblasts and collagen
What is fibrocartilage like?
Found in the annulus fibrosus, pubic symphysis
•Visible collagen fibres in matrix
•Perichondrium – fibroblasts and collagen
What is synovium?
Lines the inside of the joint capsule
•1-4 layers of synovial cells
•Type A – phagocytes
•Type B – rich in rER
•Variable shapes – squamous to cuboidal
•Richly vascular, highly innervated
What are muscle types?
Visceral (smooth) muscle
arterial wall, wall of intestine
airways of lungs
Voluntary (skeletal) muscle
skeletal muscles, larynx
diaphragm
Cardiac muscle
heart
base of great vessels
Other contractile cells
pericytes, myo-fibroblasts
myo-epithelial cells
What is smooth muscle like?
Involuntary muscle
Fusiform cells
Central nucleus
No striations
Non-branching
Where do connective tissues arise from?
Connective tissue cells arise from mesenchymal cells and haematopoetic cells
What do fibroblasts produce?
Fibroblasts produce collagens (many types, with different functions), elastins and other proteins
What are the histology of adipocytes?
What is cartilage made up of?
•Cartilage comprises chondrocytes and extracellular matrix
What are chondrocytes from?
Chondrocyres derived from chondroblasts derived from mesenchymalme. Fibre content in matrix varies between cartilage types?
What are the three types of muscle?
Three types of muscle: smooth, skeletal, cardiac with distinct histological appearances
What is the structure of arteries?
Inside:
- Lumen
- Endothelium
- basement membrane
- intima
- internal elastic laminate
- media
- external elastic lamina
- adventitia
Outside
What are the elastic arteries?
Arteries near the heart e.g. aorta, pulmonary arteries
Media contains abundant concentric sheets of elastin (seen here as thin red lines)
What are muscular arteries like?
Most arteries are muscular arteries
Media comprises layers of smooth muscle
Little elastin in the media
e.g. radial artery, splenic artery
What are muscular arteries like?
Most arteries are muscular arteries
Media comprises layers of smooth muscle
Little elastin in the media
e.g. radial artery, splenic artery
What is the general structure of capillaries?
Inside:
- Lumen
- endothelium (inside b.m)
- basement membrane
Outside:
- Pericytes
Fenestrated capillaries - endothelium incomplete
What are capillaries like?
Composed entirely of thin-walled endothelial cells with no surrounding muscle or connective tissue.
Most tissues have closed capillaries but some tissues (e.g. kidney & liver) have more “leaky” fenestrated ones
What is the general structure of veins?
Inside:
Lumen
Endothelium
Intima
Basement membrane
Internal elastic lamina
Media
Adventitia?
Outside:
Check
What are venules like?
Associated with arterioles
Thin walled
Contractile pericytes wrap around outside of endothelial cells and form a complete layer as venules get larger.
Pericytes replaced by smooth muscle as venules become veins
What are venules like?
Associated with arterioles
Thin walled
Contractile pericytes wrap around outside of endothelial cells and form a complete layer as venules get larger.
Pericytes replaced by smooth muscle as venules become veins
What are veins like?
Large veins are thick walled (compared to venules)
Thin walled compared to corresponding artery
Smooth muscle in wall may be circular or longitudinal
What are lymphatics like?
Thin walled, similar to capillaries and veins
Have valves
Do not contain blood
Contains eosinophilic lymph and may contain lymphocytes
What are the peripheral nerves like?
Composed of axons
Supported by Schwann cells
Most are myelinated – insulating sheath
Myelin produced by Schwann cells
What is the structure of a peripheral nerve?
?
What is in a myelinated peripheral nerve?
Endoneurium
Present between individual axons
Perineurium
Surrounds the groups of axons to form fascicles
Epineurium
Binds fascicles together to form nerve fibres
What are small peripheral nerve fibres?
Bundle of axons interspersed with endoneurium and
surrounded by perineurium and epineurium
Myelinated axons
Endoneurium
Perineurium
Epineurium
How is an artery diff to a vein?
Arteries have Thicker walls and smaller lumen than veins
What is myelin formed by?
Schwann cell wrapping around axon
One myelinated axon per Schwann cell, multiple Schwann cells per myelinated axon
Multiple unmyelinated axons per Schwann cell, multiple Schwann cells per unmyelinated axon
