Histology Flashcards
Eukaryotic cells
TRUE NUCLEUS
- Outer membrane
- Inner cytosol - solution of proteins, electrolytes and carbohydrates
- Cytoskeleton - determines shape and fluidity of the cells (Made from thin, intermediate filaments and microtubules)
- Membrane bound organelles within the cytosol
- Strictures in the cytoplasm which may or may not be bound by a membrane ie inclusions (CAN ONLY BE PRESENT AS TRANSIENTS) components that have been synthesise by the cell itself
Plasmalemma
Separates cytoplasm from outside environment
- Contains integral proteins
- Can exocytose and endocytose material
- Fluid mosaic
- Selectively permeable (water, oxygen, small hydrophobic molecules)
- Impermeable to charged ions
- Contains embedded cholesterol
Phospholipid bilayer
- Hydrophilic heads at outer and inner surfaces (choline is found here, phosphate is found just below the choline)
- Hydrophobic tails at centre
proteins in the plasmalemma
oReceptors oChannels oTransporteds oEnzymes oCell attachement proteins
Organelles
Small intracellular oragns with a specific function and structural organisation
mitochondria
energy production site
Rough ER
site of protein sythesis
Smooth ER
cholesterol and lipid synthesis and detoxification
golgi apparatus
modification and packaging of macromolecules
lysosomes
hydrolytic enzymes of intracellular digestion
nucleus
contains genetic code
Cytoskeleton
Microfilaments= 7cm composed of actin
intermediate filaments=>10nm composed of proteins
microtubules= 25nm composed of tubulin
Tubulin
can be alpha or beta, originaed from organising centre called centrosom. polar structures. Dynein (ATPase that moves towards the cell centre) and kinesin(ATP ase and moves towards the peripheries) attach to them and move along them
Contain stabilising proteins- microtubule associated proteins (MAPS)
nucleus
inner and outer membrane with pores. outer membrane is studded with ribosomes and continuous with the cytoplasmic rough ER
contains chromosomes
site of RNA synhesis (tRNA in the nucleus and rRNA in the nuclelus)
EUCHROMATIN
DNA that is actively undergoing transcription
HETEROCHROMATIN
DNA that is condensed and not under going transcription
Ribosomes
Formed in nucleolus, small subunits whic bind to RNA nand large subunits which catalyse formation of peptide bonds
Endoplasmic reticulum
forms a netwrok of interconnecting membrane bound compartents in the cell
rough ER
studded with ribosomes, proteins sythesis destined for insertion into membranes or secretion. Free ribosomes attaches to mRNA–>If ER signal sequence is present, growing peptide is inserted into a pore in the ER –> Growing peptide forms in the ER, signal sequence removed–> Ribosome detaches, most proteins then enter the SER
Smooth ER
Continues processeing proteins from RER, site of lipid synthesis
Golgi apparatus
composed of a group of flattened, membrane bound cisternae, vesicles arrive at golgi from SER and golgi modifies and packages macromolecules (adds sugars,Cleave some proteins, Sorts macromolecules into vesicles)
Mitochondria
composed of inner and outer membrane, inner folded to form cristae (increasing the surface area)
Generates ATP via axidative phosphoylation and the synthesis of lipids and proteins
Occluding junctions
Link cells to form diffusion barrier
Prevent diffusion
Also known as tight junctions
Anchoring/Adherant junctions
provide mechanical strength
link submembrane actin bundles of adjacent cells
Cadherin molecules bind to each other in extracellular space and to actin of cytoskeleton
Desmosomes
link submembrane intermediate filaments of adjacent cells (commonly found in the skin)
Hemidesmosomes
link submembrane intermediate filaments of cells to extacellular matrix through transmembrane proteins
communicating junctions
allow movement of molecules between cells
often termed gap junctions
each junction is circular patch studded with pores. found in epithelium, but also in smooth muscle and cardiac muscle
Endocytosis
Membrane invaginates, fuses and newly made endocytotic vesicle buds into cell
Often receptor mediated
Exocytosis
Works in reverse of endocytosis
Phagocytosis
- Bacteria binds to cell surface, cell engulfs it to form phagosome, binds with lysosome containing digestive enzymes
- When a phagosome binds with a lysosome carrying a digestive enzyme=phagolysosome
- matierial is digested
Formalim
tissue is often fixed to preserve it in as like life state as possible using this chemical that cross links proteins
Stains
H&E - haematoxylin - purple, basic dye
eosin - pink, acidic dye
tissue types
- Epithelium
- Connective tissue- froms the framework of the body, but beyond that has a dynamic role in the development, growth and homeostasis of tissues, and via fat in energy store
- Muscle- specialised to generate force by contracting
- Nervous tissue- consists of neurons and their supporting cells, serves a control function and allows for rapid communication between different parts of the body
Epithelium
- covers surfaces of body,lines hollow organs and forms glands
- all have a basal lamina
Non-vascular- nutrients from cappilaries in underlying tissues must diffused across the basal lamina
-Usually polarised - apical and basal sides differ
Functions of the epithelium
- mechanical barrier
- chemical barrier
- absorption
- secretoin
- containment
- locomotion
Epithelium cell shaped
Squamous - flattened
Cuboidal - cube
Columnar - tall and thin
Epithelium number of layers
Simple - one layer
Stratified - two or more layers
Pseudostratified - tissue appears to have multiple layers
goblet cells
single cell mucous glands
Glandular epithelia
produce secretory products such as sweat, milk, oil, hormones, mucous, enzymes and other
Endocrine
product secreted towards basal end of cell, distributed by vascular system and ductless glands
Exocrine
product secreted towards apical end of the cell- ducted glands
Connective tissue
Forms framework of body, dynamic role in development, growth and homeostasis of tissues, and energy storage (fat)
soft connective tissue
eg Tendons, ligaments, mesentery, stroma of organs, dermis of skin
Loose- loosly packed fibres separated by abundant ground substance. Plentiful
Dense- densely packed bundles of collagen fibres,Dense regular if fibres aligned, Dense irregular if fibres run in many directions
Hard connective tissue
eg bone and cartilage
Strong, flexible, compressible, semi-rigid tissue
Types of cartilage
Hyaline - articular surface, tracheal rings, costal cartilage, epiphyseal growth plates-Is a precursor of bone
Elastic- is found in the external ear, epiglottis and larynx
Fibrocartilage- is found in invertebral discs, joint capsules, ligaments
Bones
Outer shell of cortical bone makes up shaft - diaphysis
Cancellous/trabecular bone occupies ends - epiphyses
Cancellous bone: fine meshwork of bone that looks a bit like the insie of a aero bar
Blood and lymph connective tissue
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connective tissue consists of…
Extracellular matrix
-Fibres - collagen, reticular and elastic fibres
-Ground substance- amorphous, space occupying material made of huge unbranched polysaccharide molecules called glycosaminoglycans (glycoproteins)
-Tissue fluid
Cells
-Fibroblasts- widely distributed cells that produce and maintain the extracellular matrix
-Adipose cells- fat cells, in connective tissues
-Osteocytes- bone cells
-Chondrocytes- cells of cartilage
Muscle
specialised to generate force by contraction, force is movement of actin fibres over myosin fibres
Smooth muscle
involuntary and non striated
skeletal muscle
voluntary and striated, multinucleated (Nuclei are elongated at located at the periphery, just internal to cell membrane (sarcolemma))
cardiac muscle
involuntary and striated (have intercalated discs, containing multiple intercellular junctions to maintain mechanical integrity)
Nervous tissue
consists of neurons and thier supporting gells, control function and allows for rapid communication betwen diffferent parts of the body- surrounded by connective tissue coat
o Meninges in CNS
o Epineurium in PNS
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what are glia
which make sure the neurons are working and provide nourishment and repair to the cell
Types of glia:
Astrocytes-Support and ion transport
Oligodendrocytes-Produce myelin
Microglia-Provide immune surveillance
Schwann cells (PNS)-Produce myelin and support axons
Salivary glands:
Parotid (serous secreting cells)
Submandibular(mucous secreting)
sublingual
Striated ducts (usual feature)- modifies the saliva that is passing through by pumping salt out of the fluid so that it is hypotonic to blood
Layers of the oesophagus
Mucosa
- Epithelium - sits on basal lamina
- Lamina Propria - loose connective tissue
- Muscularis Mucosae - thin layer smooth muscle
Submucosa - loose connective tissue
Muscularis externa - 2 thick layers mooth muscle, inner circular and outer longitudinal layer
Serosa or adventitia - outer layer of connective tissue that either suspends digestive tract or attaches to other organs
protective mucosa
Non-keratinised stratified squamous epithelium
eg oral cavvity, pharynx, oeophagus, anal canal
Absorptive mucosa
simple columnar epithelium with villi and tubular glands eg small intestine
Secretory mucosa
Simple columnar epithelium with extensive tubular glands
eg stomach
Protective and Absorptive mucosa
Simple columnar epithelium with tubular glands
eg large intestine
In the large intestine, the outer longitudinal smooth muscle is not continuous - found in 3 muscular strips called teniae coli
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enteric nervous system
the neurons live in groups called ganglia between two muscle layers that make up the musclaris externia
what is the enteric nervous system
The enteric nervous system (ENS) is a autonomous part of the nervous system and includes a number of neural circuits that control motor functions, local blood flow, mucosal transport and secretions, and modulates immune and endocrine functions.
The goblet cells of the epithelium and the submucosal glands produce a viscous fluid that coats the surface of the airway and traps particles that are then propelled out of the airway by cilia.
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bronchus vs brochioles
bronchus- large airways with hyaline cartilage in the wall
bronchioles- small airways, no cartilage and mainly smooth muscle
Alveoli
lined with simple squamous epithelium
Liver
Lobules- hexagonal arrangement make up the liver
liver cells
hepatocytes
kupffer cells
monocytes that remain resisdent in the liver
spaces for blood flow in the liver are called
sinusoid
In each corner there is a branch of the hepatic portal vein and a branch of the hepatic artery, each delivering blood to the lobule- in the centre there is a vein that drains to the hepatic vein
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Exocrine pancreas
pancreatic digestive enzymes containing proteases, lipases and nucleases
endocrine pancreas
islets of Langerhans - produce insulin
proteases
break down protein
lipases
break down lipid
nucleases
break down DNA/RNA
blood composition
55% plasma, 45% cells
Red blood cells
no nucleus, 7 nano metres
Lifespan of about 4 months, liver and spleen remove ages RBC
Also called erythrocytes
WBC
ie luekocytes=neutrophils, eosinophils, basophils-rare) granulocytes, monocytes, lymphocytes
neutrophils
most common, has many granules in their cytomplasm, stains poorly with acidic or basic dyes and has a prominent, mutlilobed nucleus. Circulate blood in an inactive state, when activated they turn into phagocytes, activated by bacteria, inflammation and entering tissues.
Eosinophils
contain a variety of hydrolytic enzymes, important in allergic reactions and fighting parastitic infection- have affinity for red acidic dye eosin
Basophils
high affinity for basic dyes such as methylene blue, granules contain histamine, herpain, and other inflammatory mediators, effector cell in allergic reactions, they have high affinity IgE receptors
lymphocytes
round nucleus surrounded by a thin rim of cytoplasm that doesn’t not have visable granules (T AND B CELLS) arise in bone marrow. T Cells differentiate in the thymus. B cells give rise to antibody secreting plasma cells
Artery wall
Tunica intima - extends to internal elastic membrane (Endothelial cells)
Tunica media-Smooth muscle
Tunica adventitia-Supporting connective tissue
Tunica media and the tunica adventitia are separated by the external elastic membrane
Arteriole
1 or 2 layers of smooth muscle in tunica media and almost no adventitia
Capillaries
]Endothelial cells and a basal lamina
Have pericytes - connective tissue cells with contractile properties
3 types of capillaries
3 types
Continuous - muscle, nerve, lung, skin
Fenestrated - have pores - gut mucosa, endocrine glands, kidney
Sinusoidal - have large gaps - liver, spleen, bone marrow
Venules
endothelium and pericytes
veins
tunica intima, thin continuous tunica intima and a few layers of smooth muscle cells
Lymph
Smooth muscle in walls, hydrostatic pressure in the tissue and compression of the vessels by voluntary muscle, combined with the valves in the vessels produce flow
Aorta is an elastic artery because
they have many sheets of elastic fibres in their tunica media to provide elastic recoil
Verhoeffs/ masons trichrome stain
stains elastic black, collagen green and smooth muscle red
Modified van giesons stain
stains collagen red, cytoplasm yellow and elastin black
Blood separated= spinning in a centrifuge (red cells, white cells and plasma) bottom to top, once clotting factors are removed from the blood serum is left.
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Platelet hemostasis:
- Adhere
- Aggregate
- Degranulate
In second trimester the liver is main site for blood formation but by birth the bone marrow is the main site for blood formation. RBC are made from stem cells.
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