Physiology Flashcards
Half life of LH
60 mins
Half life of FSH
170 minutes (3h)
Half life of hCG
24 hours
Structure of GnRH
Decapeptide (10x peptides)
Source of cholesterol in term foetus
De novo synthesis in their own liver
Post menopausal ratio of uterus:cervix
1:1 or cervix is bigger than uterus 1:2
Largest cell in human body
Oocyte
How is magnesium excreted by the body?
Kidneys and faeces
Haldane effect
The ability of deoxygenated hemoglobin to carry more carbon dioxide (CO2) than in the oxygenated state, reflecting a tendency for an increase in pO2 to diminish the affinity of Hb for CO2
Umbilicus: how many arteries/ veins?
2 arteries (deoxygenated blood)
1 vein (oxygenated blood
When can the quadruple test be done and what does it include?
What indicates Down’s syndrome?
Second trimester (14-20 weeks)
Beta hCG, inhibin A, AFP and estradiol
Raised bHcG, raised inhibin A
Low AFP and low estradiol
What does the combined test involve and when can it be done?
Results suggestive of downs/ patau/ Edwards?
Nuchal translucency & PAPP-A/ beta hCG
11+2 until 14+1 gestation
Downs: Raised NT, low PappA, raised bhCG
Edwards & Patau: Raised NT, low PappA and bhCG
What happens to 2,3 DPG in pregnancy?
Increased concentration (by 30%) –> decrease in maternal red cell O2 affinity, facilitating transport of oxygen across placenta
How much does total lung volume decrease by in pregnancy?
200ml
What happens to expiratory reserve volume in pregnancy? (therefore functional residual capacity)
It reduces
How does minute ventilation/ volume change in pregnancy?
It increases by 40%
Difference between fetal Hb and adult Hb
Fetal Hb has higher affinity for O2 and can resist denaturation by strong acid/ alkali more than adult Hb
Path of sperm penetration
Corona radiata
Zona pellucida
Perivitelline space
Plasma membrane
Face presentation diameter
9.5cm (when hyperextended)- submento-bregmatic
Coagulation factors that increase during pregnancy
all except XI and XIII
3 fold increase in cortisol in pregnancy. Mechanism?
Increased unopposed oestrogen
Prolactin levels in pregnancy compared to pre-pregnancy
10 fold increase
Changes in blood composition during pregnancy
- Platelet count reduces
- Increased coagulation factors (VII, VIII, IX, X, XII)
- Increased fibrinogen
- Increased ESR
- Protein S levels reduce (physiological anticoagulant)
- Reduced XI and XIII
- Antithrombin III and protein C are unchanged
How much does renal blood flow increase by in pregnancy?
How much does eGFR increase by?
How much do kidneys increase in size?
50-60%
eGFR: 40% (by end of 1st trimester)
Around 1cm
Lung volume changes in pregnancy
Functional residual capacity reduced by term by approx 20%.
Total lung capacity reduced by approximately 5% (200ml)
Residual Volume reduced by approximately 20%- leading to reduction in IRV and ERV
Tidal volume is increased by approximately 50%.
Minute ventilation increase by about 50% during 1st trimester.
Oxygen Consumption increases by approx 20% (50ml/min)
FEV1 and FVC are unchanged
Tidal volume unchanged
RR unchanged
PCO2 decreases.
PO2 increases.
pH remains normal or increases slightly (renal compensation: HCO3- decreases)
Typical volume increase from a non-pregnant to term uterus?
10ml to 5000ml
Typical weight of a non-pregnant vs pregnant uterus
40-50g
1100-1200g
Calcitonin production causes what response
Inhibits calcium absorption by the intestines
Inhibits osteoclast resorption of bone
Stimulates osteoblast activity in bone to sequester calcium
Inhibits renal tubule resorption of calcium
Increases urinary calcium excretion
Primary form of fetal haemoglobin
<12 weeks, primary form is Embryonic Hb (Hb Gower 1)
> 12 weeks, fetal Hb
By 6 months, adult Hb is primary form >98%
What is reabsorbed in the PCT?
Glucose
Amino acids
Carboxylate
Bicarbinate
Phosphate
Potassium
Sodium
Urea
Calcium, magnesium, water
99% of body calcium is in what form?
Calcium phosphate (in bone- hydroxyapatite)
Cardiovascular changes in pregnancy
Blood volume increases by 30%: Plasma increases by 40-50% & red cell mass by 25-30%
Heart rate rises by 15 beats/min above baseline
Stroke volume increases by 25-30%
Cardiac output increases by approximately 30-50% (Increased by 1.5L at term, 30% of which goes to uterus- 400ml/min)
Systemic vascular resistance (SVR) decreases by 20-30%
Diastolic blood pressure consequently decreases between 12 and 26 weeks but increases again to pre-pregnancy levels by 36 weeks
A third heart sound after mid-pregnancy
Systolic flow murmurs
ECG changes:
- LAD (around 15 degrees)
- Inverted T wave in lead III
- a Q wave in leads III and aVF
Average lifespan of RBC/ platelet/ WBC
RBC: 120 days
Plt: 5-9 days
WBC: 2-5 days
At what stage of fetal development does fetal Hb replace embryonic Hb?
10-12 weeks
Effect of vasopressin (ADH)
Promotes water retention by:
- Insertion of aquaporins into collecting duct and DCT
- Increased activity of urea transport proteins in the collecting duct promoting urea flow out of the collecting duct and water via osmotic gradient
- Increased sodium reabsorption across the ascending loop of Henle
How is ADH/ vasopressin secreted?
Receptors in the hypothalamus detect increases in serum osmolality and stimulate the posterior pituitary to secrete ADH
During the inflammatory stage of wound healing, what is the predominant cell type found? (D3-4)
Macrophages
Typical oxygen consumption in a non-pregnant vs pregnant woman (75kg)
Non-pregnant: 250ml/min
Pregnant, increases by 20%: 300ml/min
Changes to biliary physiology in pregnancy
Due to increasing circulating oestrogen and progesterone:
- Inhibition of canalicular excretion leading to cholestasis and itching
- increased cholesterol synthesis
- Increased bile acid concentration (increased lithogenic index) and increased risk of gallstones
- Increased spider naevi (50% patients)
- Incomplete gallbladder emptying
How is the intrinsic/ extrinsic pathway activated in the clotting cascade?
Extrinsic: tissue factor
Intrinsic: damaged endothelium
Body composition
Intracellular fluid = 40% body weight, 60-70% of body water
ECF = 20% of body weight,
30-40% of body water
ECF = plasma & interstitial fluid
Plasma volume + around 3L (5% body weight)
Intracellular/ Extracellular anion/ cation
ICF cation: K+
ICF anion PO4-
ECF cation: Na+
ECF anion: Cl-
When does oocytogenesis complete?
Either at birth or shortly before (3rd trimester)
When does ootidogenesis complete?
Comprises both meiotic divisions.
First meiotic division halts until puberty
Second meiotic division only completes at fertilisation
Increase in oxygen consumption in pregnancy at term?
50ml/min
At what gestation does the maximum physiology anaemia occur?
32 weeks
How much does ALP increase in pregnancy?
May reach 3x upper limit of normal
Average size of:
- Resting follicle
- Prenatal phase follicle
- Antral phase follicle
- Pre-ovulatory phase follicle
Resting follicle
0.02mm
Preantral phase follicle
0.2mm
Antral phase follicle
2mm
Pre-ovulatory phase follicle
20mm
What is the name of the fluid filled space in a follicle?
Antrum
What proportion of primordial follicles undergo atresia to create a primary follicle?
99%
what is the structure between the theca cells and the mural granulosa?
Basal lamina
Where are the cumulus granulosa cells?
They surround the oocyte
Which part of spermatozoa has highest concentration of mitochondria?
Middle piece
Summary of spermatogenesis
Spermatogonium (2n) undergoes mitotic division to produce daughter spermatogonium (2n).
Daughter spermatogonium undergo growth and differentiation to produce primary spermatocyte (2n)
Primary spermatocyte undergoes Meiosis I to produce 2x secondary spermatocytes (1n)
Secondary spermatocytes undergo meiosis II to produce 4x (1n) spermatids.
Spermatids undergo spermeogenesis to produce spermatozoa.
Primary anions in blood
Bicarbonate and chloride
When does the LH surge happen and when does ovulation occur in relation to this?
LH surge occurs 24h post oestrogen surge.
Ovulation occurs 16-18h post LH surge.
Which hormone rises prior to onset of menses?
FSH
Sources of inhibin
Granulosa cells
Corpus luteum
Half life of prolactin
20 minutes
What impact does estradiol have on prolactin?
It increases its production
Lifespan of ovum and sperm
Ovum <72h
Sperm <5d
Corpus luteum
- What hormones does it produce?
- What receptors/ cells does it have?
- How long does it persist for?
- When is it no longer essential to a pregnancy?
Produces
Progesterone, Oestrogen , Relaxin, Inhibin A, Inhibin B
Has LH receptors
Contains lipid laden cells
Persists for 6 months.
Placenta takes over function after 3/12
No longer essential to pregnancy at 6 weeks gestation
When does regression of corpus luteum happen in relation to menses?
3-4 days prior, allowing levels of progesterone/ oestrogen and inhibin to fall
Hormones of spermatogenesis
GnRH – starts age 10 (Testicular size increase is first sign of puberty)
FSH stimulates spermatogenesis in seminiferous tubules Sertoli cells
LH acts on leydig cells, stimulating testosterone production
Inhibin produced by Sertoli cells in response to too much spermatozoa inhibits FSH
Definition of delayed puberty and causes
Delayed puberty: no increase in testicular volume (i.e. <4 ml) by the age of 14 years in boys and no breast development by the age of 13.5 years in girls.
Causes:
Constitutional (90%)
Low body weight (<50kg)
Hypogonadotrophic hypogonadism (Kallman’s syndrome, hypopituitarism)
Hypergonadotrophic hypogonadism (Klinefelter’s 47XXY, Turner’s 45X0, Gonadal damage)
Precocious puberty definition and causes
The development of any secondary sexual characteristic before the age of 8 years in girls and 9 years in boys.
Constitutional
Cerebral tumour
Hypothyroidism
Sex steroid excess (CAH, leydig tumour male, granulosa tumour female, exogenous)
What does cervical ripening depend on?
What biochemical changes happen during parturition?
PGE2
Cytokines (IL-8)
Neutrophils
Collagenases and elastase
Realignment of collagen
- NO withdrawal
- Progesterone withdrawal and switch to type 2 P receptors
- Increase in placental release of CRH and oestrogen
- Upregulation of oxytocin receptors
- Increase in PG synthesis in the uterus and fetal membranes
- Increase in IL-1 and IL-8
What occurs in the foetus during parturition?
Increase in CRH, ACTH and Cortisol/DHEAS leads to fetal lung maturation and also labour
This causes increased maternal oestrogen and oxytocin receptors –>
Augments oxytocin and PG F2A
What happens to myometrial cells in labour?
Formation of gap junctions (promoted by estradiol (E2), which rises relative to progesterone)
Role of catecholamines in labour
B2 adrenergic agonists inhibit labour
A2 adrenergic agonists cause contraction
What is the Ferguson reflex?
Pressure to cervix and vagina causes spurts of oxytocin release
When do women return to menses post- delivery?
Breastfeeding women return to menses at 28 weeks PP
Non breastfeeding women return to menses at 9 weeks PP
Lifecycle of a spermatazoa
64 days
Summary of oogenesis
Oogonium undergo mitosis in utero to produce around 2 million at the time of birth.
They undergo growth and differentiation to become primary oocytes.
Primary oocytes (2n) undergo meiosis I to produce 1x secondary oocyte (1n) and 1x polar body (1n). Meiosis I is arrested at prophase until ovulation.
Secondary oocytes undergo meiosis II to produce a mature ovum (1n) and a second polar body (in).
Meiosis II is arrested at metaphase until fertilisation.
What is secreted into the PCT?
When substances are removed from the blood and transported into the PCT
- Organic acids & bases e.g. bile salts, oxalate, catecholamines
- Hydrogen ions (to maintain acid-base balance)- exchanged for bicarbonate and sodium
- Drugs/ toxins
What acid-base disturbance does diarrhoea typically cause?
Metabolic acidoses with normal anion gap
How is anion gap calculated?
[Na+] + [K+] - [HCO3-] - [Cl-]
Coagulation cascade
Occurs via the intrinsic or extrinsic pathway
- Intrinsic pathway is initiated by exposure of blood to negatively charged surfaces such as collagen in vivo or glass in vitro
- Extrinsic pathway is initiated by tissue thromboplastin which is released after tissue damage (endothelial)
Both pathways result in the activation of factor X
Prothrombin is then converted to thrombin
Thrombin converts solute fibrinogen into insoluble fibrin
Apart from the first two steps of the intrinsic pathway, all steps require calcium.
CItrate and oxalate remove calcium and prevent clotting.
Natural anticoagulants
Anti-thrombin III
Protein C
Protein S
Heparin
The smoothness of the endothelial surface is important in preventing intravascular coagulation
Tissue thromboplastin activates the extrinsic pathway while plasmin causes clot lysis but does not prevent clot formation
Where are clotting factors synthesised?
Most are synthesised in the liver.
Factor VIII is synthesised by liver sinusoidal cells and other endothelial cells
How are free fatty acids transported across cell membranes?
Passive diffusion
How is glucose transported across the placenta?
Facilitated diffusion
Examples of bile acids
Synthesised from
Function
Cholic acid
Chenodeoxycholic acid
Can then be conjugated with taurine or glycine to form glycol- or tauro- conjugates
Synthesised from cholesterol
Have an emulsifying effect on fat in the intestine (decreasing surface tension)
Play important role in fat absorption
Calculating mean arterial pressure
Diastolic pressure + (1/3 of pulse pressure)
Pulse pressure = systolic - diastolic
Where does potassium absorption occur in the nephron?
PCT
LoH
Collecting ducts
Which enzyme in the renal tubular cells is responsible for production of ammonia?
Phosphate-dependent glutaminase
Diameter of fetal skull:
- OA with complete flexion
- OA without complete flexion
- OP
- Face presentation with head extended
- Incompletely extended face presentation
- Brow presentation
Breech presentation
- Bi trochanteric diameter
- Bi acromial diameter
OA with complete flexion: 9.5cm
(suboccipito-bregmatic)
- OA without complete flexion: 10cm +
(suboccipito-frontal) - OP: 11.5cm
(Occipital-frontal) - Face presentation with head extended: 9.5cm
(Submento-bregmatic) - Incompletely extended face presentation: 11.5cm
(Submento-vertical) - Brow presentation: 13.5cm
(Mento-vertical) - Bi trochanteric diameter: 10cm
- Bi acromial diameter:11cm
Change in colloid osmotic pressure during pregnancy compared to pre-pregnancy
10% increase
What happens to aldosterone secretion in pregnancy
Increases
Sickle cell syndrome- Hb
Autosomal recessive
Single base mutation of adenine to thymine producing a substitution of valine for glutamine at the 6th codon of the beta-globing chain
Homozygous (Hb SS) = SCD
Heterozygous (HbAS)- trait. Levels of HbA2 increased.
What is associated with increased fetal surfactant production?
Decreased?
Increased:
Hypertensive disorders of pregnancy, malnutrition, placenta praaevia, drug addiction, PROM, IUGR, females, haemoglobinopathy
Decreased:
DM, anaemia, polyhydramnios, hypothyroidism, males, twins, is-immune disease, cold stress
How is fetal blood volume related to weight
Approx blood volume in a term newborn?
10-12% body weight
300ml
Which is the most abundant carbohydrate in breast milk?
Lactose
Change in maternal cardiac output in labour and post delivery
Increases by 40%
(First stage, increases by 10-25%, second stage by 25-50%)
Post delivery, increases by 10-20%
When are phagocytic cells present in the foetus?
During the first trimester
Most common solid tumour in the neonate?
Neuroblastoma
Cells in proximal duodenum that secrete alkaline rich mucus
Brunner’s cells
Protein absorption by the PCT is by
Pinocytosis
How are amino acids transported across the placenta
Secondary active transport
When does GFR reach its maximum during pregnancy
36 weeks
At what gestation does fetal urine become the major contributor to Amniotic fluid volume
18 weeks
At what gestation does the formation of definitive alveoli take place?
36 weeks
How long does it take the placental bed to acquire a new endometrial layer?
Within 1 week the uterine cavity has a new endometrial layer, with the exception of the placental bed which takes around 3 weeks.
Which subunits are found in HbF?
Alpha and gamma (2 of each)
When are primordial follicles at their max number in a female foetus?
20 weeks
JVP waveforms
X wave occurs at the end of atrial systole.
A wave = atrial systole
C wave = ventricular systole
V wave = atrial filling against closed tricuspid valve
Y descent occurs following tricuspid valve opening.
