Histology Flashcards
Describe the structure of an artery
Blood flows through lumen which is bound by a basement membrane on which there is endothelium (Simple squamous)
This is surrounded by connective tissue INTIMA
This is surrounded by internal elastic lamina (Elastic tissue =)
Around this is the MEDIA which contains some smooth muscle then there Is the external lamina and the adventitia on the outside
The closer an artery is to the heart, the greater the amounts of what found in its wall?
Elastic tissue
How is the tendency of the aorta to over distend during systole overcome by its structure?
Media contains abundant concentric sheets of elastin arranged in circumferential sheets between layers of smooth muscle
Which blood vessels are the resistance arterioles of the circulatory system?
Arterioles
Define an arteriole
Defined as having 3 or fewer muscle layers in their media or are up to or less than 100um in diameter
Lack an external elastic lamina and the internal elastic lamina is poorly defined
Describe the structure of capillaries
Hace endothelial cells on a basement membrane and are line by pericytes forming discontinuous layer which becomes continuous as capillaries get larger
Where the vascular endothelium is incomplete there are gaps called fenestrations
What is the main structural differences between arterioles/arteries and veins
Arteries and arterioles have thicker muscular walls and a thinner lumen than veins
Describe the structure of veins
Have a wide lumen surrounded by a basement membrane upon which is a layer of endothelium. There is then a thin layer of intima, and internal elastic lamina then media and adventitia
What is the main structural difference in the walls of arteries and veins
Veins don’t have an external elastic lamina
Describe the structure of venues
Wall consists of endothelium reinforced by connective tissues with contractile pericytes around the outside. These pericytes are replaced by smooth muscles as the venues become veins
Describe the structure of lymphatics
Thin walled with valves. Walls contain mixture of collagen and elastin with little smooth muscle and are typically filled with an amorphous colloid plasma that stains pink with H and E
What are the two parts of the nervous system
CNS - brain and spinal cord
PNS - axon processes to target organs an tissues
Myelin is produced by what cell in the peripheral nerves
Schwann cells
Do axons stain with H and E
No
Define endoneurium
Between individual axons
Define perineurium
Surrounds groups of axons to form fascicles
Define epineurium
Binds fascicles together to form nerve fibres
What is found in a neuromuscular bundle?
Nerve, arteriole and venule
What stain is used to identify myelin?
Silver stain
What are the main components of connective tissue
Elastin, collagen, amorphous material which has a high molecular weight, strongly hydrophilic and negatively charged to retain water
GAG’s are synthesised by what cell types?
Epithelial, muscle, cartilage and bone but mostly by fibroblasts
Define soft connective tissue
Flexible and gel like - divisible into fibrous or fatty connective
Define hard connetive tissue
Forms of bone
Define fibrous connective tissue
Contains large numbers of collagen, elastin and reticulin fibres
Define loose irregular fibrous connective tissue
Contains few randomly orientated fibres
Define dense irregular fibrous connective tissue
Contains large number of fibres with little amorphous material
Define regular dense fibrous connective tissue
Fibres arranged in parallel bundles
Define fatty connective tissue
Contains mainly fat cells with intervening blood vessels, particularly capillaries
Where are connective tissue cells mainly derived from?
Mesenchymal cells
What are the main cell types found in connective tissue?
Adipose
Fibroblasts/Fibrocytes
What are the main visible fibres found in connective tissue?
Collagen
Elastin
Reticulin
What are the main components of ground substance
Proteoglycans
Glycosaminoglycans
Laminin/Fibronectin (Invisible fibres)
Does ground substance stain with H and E?
No, appears as white space
What cell type secretes collagen
Fibroblasts
What are the type 1 collagens
Skin, bone, teeth and organ capsules
What are the type 2 collagens
Cartilage
What are the type 3 collagens
Liver, bone marrow and spleen
What are the type 4 collagens
Basement
What are the type 5 collagens
Placenta
Describe the structure of a tropocollagen subunit
Three linear polypeptide chains wound together in an alpha helix
Give an example of regular dense connective tissue
Tendon
Give an example of irregular dense connective tissue
Penile fascia
Describe reticulin
type 3 collagen forms supporting scaffold for liver, bone marrow, kidney, spleen and lymph nodes
Is reticulin visible on H and E
No, needs a silver stain that makes the collagen appear as black lines
Van Geisons stain will stain elastic fibres and sheets what colour?
Dark brown
Describe white adipose
Large cells with a single fat globule in each cell and appear as an empty white space
What is the function of white adipose?
Protects the vital organs and serves as an energy store
Describe brown adipose tissue
found across the shoulders and backs of newborns
Pink foamy appearance
What is the function of brown adipose
Thermal regulation - generates heat upon breakdown
Where is cartilage derived from
Undifferentiated mesenchymal cells
Describe the structure of cartilage
Chondroblasts become embedded within a dense GAG matrix containing variable amounts of collagen and elastic tissue - the chrondroblasts mature into chondrocytes which are unable to migrate through the matrix
What is the fibrous capsule surrounding cartilage called?
Perichondrium which contains undifferentiated progenitor cells that can differentiate into chondroblasts
Give an example of a glycosaminoglycans
Hyaluronic acid
Give two examples of proteoglycans
Chondroitan sulphate
Keratan glycan
Give three types of cartilage
Hyaline
Elastic
Fibro
Where is hyaline cartilage found
In synovial joints
Rings of the trachea and the cartilage of the larynx
Where is elastic cartilage found?
Pinna of the ear
Epiglottis
Where is fibrocartilage found
In the annulus fibrosis in the intervertebral discs and in the pubic symphysis
Give three locations of visceral smooth muscle
Wall of the intestine
Arterial wall
Bronchioles of the lung
Give three locations of voluntary skeletal muscle
Skeletal muscles
Larynx
Diaphragm
Other than muscle name three other contractile cell types
Pericytes
Myo-Fibroblasts (Scar formation)
Myo-epithelial cells (Expression of milk during lactation)
Describe the structure of a gap junction
Consists of 6 connexion proteins that link the interior of adjacent smooth muscle cells with a guarded central pore that permits the passage of small molecular weight molecule, electrically coupling them
What are the functions of epithelial cells
Protection - skin
Absorption - gut
Secretion - pancreas, liver and GIT
Describe the structure of a simple epithelia
Single layer of cells on a basement membrane
What function are simple epithelia associated with?
Absorption and secretion
Describe the structure of stratified (Compound) epithelia
Two or more layers of cells on a basement membrane
What function is associated with stratified epithelium
Protection - found in areas of the body that experience frictional and abrasive forces such as the skin, mouth, throat, oesophagus and vagina
What is the simple squamouss epithelium that lines the blood vessels called?
Endothelium
What is the simple squamous epithelium that lines outside the lungs called
Mesothelium
What is the simple squamous epithelium that lines abdominal organs called
Peritoneum
Describe the structure of simple cuboidal epithelium
Single layer of cells with similar height and width on a basement membrane with a central spherical nuclei
Where are simple cuboidal epithelium found?
Occur in the ducts of glands such as sweat, salivary and pancreatic (Exocrine glands)
Describe the structure of simple columnar epithelium
Single layer of cells that are taller than they are wide sat on a basement membrane with an spheroidal nucleus that’s nucleus is perpendicular to the base of the cell - may or may not have microvilli or villi to increase surface area
Where are simple columnar epithelium found?
Lining the stomach, intestines and uterus
Where are microvilli found?
Gut enterocytes
Where are villi found?
Respiratory tract
Describe the structure of microvilli
Projections on the luminal surfaces of absorptive cells such as columnar epithelium that increase SA and are maintained by a core of actin filaments. covered in a rich glycoalyx and goblet cells
What stain is used to stain columnar epithelial cells a dark magenta
PAS
Describe the structure of cilia
0.2um motile projections on luminal surfaces of cells that contain contractile proteins that enable the wafting of mucus
Where are cilia most commonly found?
Airways of the nose, larynx, bronchial tree and Fallopian tubes
What is the purpose of keratin?
Waterproofs cells
Where is stratified squamous non-keratinising epithelium commonly found?
Mouth, oropharynx, oesophagus and vagina (Wet areas)
Where are keratohyaline granules found?
At the boundary between living epithelial cells and dead pink keratinising layers
Describe the structure of pseudo stratified epithelium
Single layer of cells of variable height mimicking multiple layers but all the cells are in contact with the basement membrane
Where is pseudo stratified epithelium most commonly found?
Trachea and the bronchi
How are cells replaced in stratified epithelium
Vertical migration
How are cells replaced in pseudo stratified epithelium
Lateral migration
Describe the structure of urothelium
Looks stratified but there is a surface layer of umbrella cells (3-7layers thick) that is not in contact with the basement membrane
Name two proteins found in the basement membrane?
collagen IV
Fibronectin
What are the two types of epithelial junction
Occluding (tight) junctions
Desmosomes (Anchoring junctions)
Describe the structure of occluding junctions
Band like fusions between cells that are impervious to molecules
Describe the structure of desmosomes
Plaques that form physical joins between cells and connect the cytoskeletons of adjacent cells
What is the function of desmosomes
To spread mechanical forces across several cells
What do adherent junctions connect
Link actin filament network between adjacent cells to the extracellular matrix
What do desmosomes connect
Intermediate filament networks of adjacent cells
What do hemidesmosomes connect
Intermediate filament network of cells to the extracellular matrix (Basement membrane)
Epithelial cells that secrete protein have what characteristic intrinsic organelles
Large nuclei and abundant endoplasmic reticulum
Mucin secreting epithelial cells have what characteristic intrinsic organelles
Expanded Golgi system
Steroid secreting epithelial cells have what characteristic intrinsic organelles
Smooth endoplasmic reticulum
Define apocrine
Secrete by budding
Define endocrine
Secrete directly into the blood
Define holocrine
releasing a secretion that is the product of the degradation of cell
Define exocrine
Secrete by passage of liquid across membranes
What percentage of blood is cellular
44%
What percentage of blood is plasma
56%
What are the components of plasma
Water Salt and minerals plasma Proteins (Albumin, globulins and fibrinogen) Hormones and signalling molecules Clotting factors
Define blood serum
Plasma minus the clotting factors
What stain is used to examine the composition of blood
Romanowsky stain
What is the lifespan of a red blood cell
120 days
Where are RBC produced
Liver (Foetus) and bone haematopoeitic marrow
What is a reticulocyte
An immature RBC that still has some ribosome remnants
Describe the structure of RBC
Enucleate Biconcave 6.5-8.6um in diameter Major protein is haemoglobin Major protein of endoskeleton is spectrin
Where are RBC normally destroyed
Liver and spleen
Define a granulocyte
Contains visible granules in cytoplasm
Which leucocytes are granulocytes
Neutrophils
Eosinophils
Basophils
Define granulocyte
No visible granules in the cytoplasm