Principles Flashcards
Describe the timeline of foetal development
1) Gametogenesis
2) Fertilisation
3) cleavage
4) gastrulation
5) formation of body plan
6) organogenesis
What is gametogenesis
Formation of gametes (egg/sperm)
Why does meiosis need to occur
To form haploids with half the amount of normal chromosomes so that when the gametes (haploids) join together, they would have a complete chromosome set instead of missing or having extra pairs
When does oogenesis begin
During foetal stage
When does oogenesis end
After menopause
The number of total oognoia during the female’s whole lifetime is determined
During foetal stage
Describe oogenesis
1) Primordial germ cell undergoes mitosis to form oogonia
2) oogonia forms primary oocytes
3) Primary oocyte stays dormant till puberty
4) Primary oocyte undergoes 1st meiotic division to form secondary oocyte
5) secondary oocyte undergoes 2nd meiotic division, forming definitive oocyte (haploid)
When does spermatogenesis occur
Begins at puberty and continues throughout life
Describe spermatogenesis
1) spermatogonia undergoes mitosis
2) one of the cell will be used to replenish spermatogonia the other undergoes mitosis
3) The cell that undergoes mitosis produces primary spermatocytes
4) Primary spermatocytes then undergoes meiosis to form secondary spermatocytes
5) secondary spermatocytes undergo 2nd meiosis -> spermatids
6) Spermatids undergo spermiogenesis to form spern
What happens to the fertilised egg after fusion of sperm and egg
Membrane thickens
Sperm receptors are shed
This prevents other sperm from entering
What is cleavage
Period of mitotic division to form blastomeres -> forms morula -> forms blastula
Feature of blastomere
There is no increase in overall size, the cells become smaller and smaller after each division
When does blastula form
When fluid filled blastoceal cavity forms
What happens to the cells in blastula
Separated into 2 groups
1) trophoblast: cells that form the placenta
2) Embryoblast: cells that form the embryo
What is gastrulation
The process by which 3 different layers are formed in the embryo
What are the 3 different layers formed in the embryo during gastrulation
Ectoderm
Mesoderm
Endoderm
Which layer in gastrulation is the outer layer of the embryo
Ectoderm
Which layer in the embryo during gastrulation is the inner layer
Endoderm
Ectoderm is used to form
Skin
Nervous tissue
Mesoderm is used to form
Skeletal muscles Dermis (middle layer of skin) Bone Heart Urogenital system
What happens during formation of body plan
Embryonic folding occurs
When does gastrulation occur
Week 3
When does formation of body plan occur
17 days after fertilisation
What happens in organogenesis
The 3 germ layers forms organs as the cells undergo differentiation and become specialized
Where does fertilisation occur
Ampulla
What does the penetration of sperm into egg cell trigger
The secondary oocyte to undergo 2nd meiosis to form definitive haploid
Cortical granules in the oocyte to release contents to prevent further entry by other sperm cells
What is the layer that surrounds the blastomeres called
Zona pellucida
What is considered as morula
When there are more than 16 blastomeres
What is blastocyst hatching
Blastula hatches out of zona pellucida to allow increase in growth and implantation
Where does the blastula attach to after blastocyst hatching and how
Attaches to the posterior or anterior endometrium epithelium by trophoblasts
When does implantation of blastula occur
On day 6
What is corpus luteum
A temporary endocrine structure that releases progesterone hormone to maintain lining of uterus for implantation
Corpus luteum is developed from
Empty follicle (follicle ruptures to release oocyte)
Embryoblast separates into which 2 layer s
Epiblast
Hypoblast
Tophoblast separates into which 2 groups
Cytotrophoblast
syncytiotrophoblast
Function of syncytiotrophoblast
Allows implantation
Secrete hCG to stimulate corpus luteum to release progesterone
What closes the endometrium after implantation has been completed
Fibrin coagulum
What are the 2 cavities formed by the 2 layers of embryoblast
Primitive yolk sac
Amniotic cavity
Which embryoblast layer forms the primitive yolk sac
Hypoblast
What are lacunae
Vacuoles in syncytiotrophoblast layer which allows maternal blood to diffuse into the embryoblast
What structure eventually forms the umbilical cord
Connecting stalk
How is definitive yolk sac formed
When a second wave of hypoblast migrate
What is chorionic cavity and how does it form
Chorionic cavity is the cavity surrounding the embryo
It forms as extraembryonic mesoderm develops and degenerates around the bilamnar embryonic disc (epiblast and hypoblast layers)
When does primitive streak form
Day 15
What is primitive streak and where is it
Primitive streak is thickened epiblast that forms in midline at caudal end.
Function of primitive streak
Release signaling molecules
Allows movement of epiblast cells to form the 3 germ layers
Determines body axes
3 regions of mesoderm
Paraxial
Intermediate
Lateral
Subregions of lateral mesoderm
Somatic layer
Visceral layer
What is between the left and right mesoderm layers and what is its function
Notochord
Precursor of spinal cord
Fate of visceral (lateral) mesoderm
Heart
Smooth muscle
Mesothelial covering organs
Fate of somatic (lateral) mesoderm
Dermis (middle layer of skin)
Lining of body wall
parts of limbs
Fate of paraxial mesoderm
Axial skeleton
Skeletal muscle
parts of dermis
Fate of Intermediate mesoderm
Kidney and ureter
Gonads
Fate of endoderm
Lining of the gut tube
Lining of resp. tract
lining of bladder and urethra
What is flucloxacillin prescribed for
Cellulitis
Infective endocarditis caused by staphylococcus aureus
Flucloxacillin is only used for which 2 bacteria
Staphylococcus
Streptococcus
Examples of beta lactam antibiotics
Penicillin
Cephalosporins
Temocillin
Examples of penicillin
Amoxicillin Penicillin Flucloxacillin Co-amoxiclav Piperacillin / tazobactam
Example of cephalosporin
Ceftriaxone
Which penicillin is resistant to beta lactamase
Co-amoxiclav
Piperacillin / tazobactam
Components of co-amoxiclav
Amoxicillin + clavulonic acid (beta lactamase inhibitor)
Bacteriostatic antibiotics
Macrolides
Tetracyclines
How does beta lactam antibiotics work
They have similar structure to D-Alanine D-Alanine so can irreversibly bind to PBP (penicillin binding proteins; transpeptidase)
This prevents cross links from forming between new chains formed during cell wall synthesis
Causes a hole in cell wall -> cell lysis
Temocillin is only used against
Escherichia (e.g. e.coli)
Salmonella
Enterobacter
Are cephalosporins narrow or broad spectrum antibiotics
Broad
Why are cephalosporins not really used anymore
Because it is a broad spectrum antibiotic, it can wipe out a lot of bacteria in the gut, reducing competition for C.difficile which allows overgrowth of C.difficile, causing gastroenteritis
Examples of glycopeptide antibiotics
Vancomycin
Teicoplanin
Are glycopeptides beta lactam antibiotics
No
Mechanism of action of glycopeptide
Binds to end of D-Alanine D-Alanine, prevents it from binding to PBP
Mechanism of action of macrolides and tetracycline
Binds to 30s subunit of RNA (tetracycline) or 50s (macrolide), preventing protein synthesis
Why are macrolides and tetracycline bacteriostatic
Because protein synthesis can resume after these drugs have been removed
Examples of macrolides
Clarithromycin
Erythromycin
Example of tetracycline
Doxycycline
Example of aminoglycosides
Gentamicin
Are aminoglycosides bacteriocidal or bacteriostatic
Bacteriocidal
Antibiotics that interfere with protein synthesis
Macrolide
Tetracycline
Aminoglycoside
Effect of high serum level of gentamicin
kidney and renal damage (gentamicin toxicity)
A cause of unconjugated hepatic jaundice
CN VIII damage (vestibulocochlear nerve - transmits sound)
Where are macrolides excreted
Via the liver
Tetracycline should not be used in
Infants / children / pregnant women
Antibiotics that affect the nucleic acids
Metronidazole
Rifampicin
Fluoroquinolone
What does rifampicin inhibit
transcription
What does metronidazole cause
Loss of helical structure of DNA and strand breakage in DNA
How is metronidazole activated
Reduction activation by obligate anaerobes
Side effect of metronidazole
Metallic taste
furred tongue
IgA is found in
breast milk Saliva Tears Sweat Mucous
What is holoenzyme
Apoenzyme + cofactors
What is apoenzyme
An enzyme that requires a cofactor but is not bound by one
Immunoglobin responsible for neonatal immunity
IgA
Immunoglobin responsible for foetal immunity
IgG
How is IgG transferred to foetus
Across the placenta directly into foetal blood circulation
Which immunoglobin is the first Ig produced during a humoral immune response
Pentameric form IgM
2 forms of IgM
Monomeric
Pentameric
Where is monomeric IgM found
on B cells, acting as B cell antigen receptor
Most abundant immunoglobin found in blood
IgG
Which immunoglobin mediates type 1 hypersensitivity
IgE
Which immunoglobin is dominant in secondary immune response
IgG
Which immune cells are responsible for killing worms
Eosinophils
Mast cells
Which immune cells are responsible for killing virus
T lymphocytes
B lymphocytes
Which immune cells are responsible for killing protozoa
T lymphocytes
Eosinophils
Which immune cells are responsible for killing fungi
phagocytes
T lymphocytes
eosinophils
Which immune cell has kidney bean shaped nucleus
Monocytes (precursors of macrophages)
Which immune cell has irregular shaped nucleus
Neutrophil
Immune cells that have granules in cytoplasm
Neutrophil
Mast cells
Eosinophils
Basophils
Which immune cells do not have granules
Monocytes
Lymphocytes
Which immune cell has bilobed nucleus
Basophil
Eosinophil
Which immune cell has the highest proportion of total WCC
Neutrophils
How to differentiate between eosinophil and basophil
Both have bilobed nucleus but the bilobed nucleus of basophils is masked by granules
Where are MHC class II molecules found
Macrophage
Dendritic
B lymphocytes
Transendothelial migration
1) margination - neutrophils fall out of axial flow of blood due to slower blood flow so neutrophils move towards the periphery (next to endothelium)
2) Pavementing - Neutrophils bind to the endothelial wall by adhesion molecules and flatten against the wall
3) Rolling - neutrophils roll along the endothelium
4) Diapedesis - migration of neutrophils across the endothelium
5) neutrophils move to site of infection via chemotaxis
What are the changes to blood flow and vasculature during inflammation
Vasodilation -> increases blood flow
Blood flow slows
What are the changes in blood flow and vasculature during inflammation
Vasodilation - increases blood flow
Blood flow slows down
