Physiology Flashcards
Which event occurs 1 day after LH surge?
Ovulation
What is the site of ovulation?
Ovary
Where is the site of fertilisation?
Fallopian tube
At which day does the blastocyst enter the uterine cavity?
Where does this occur?
Day 3-5
Uterus
What day does implantation occur?
Day 6-7
Which day does hCG get released?
Where does this occur?
9-10
Trophoblastic cells
State the order of potency regarding stem cells.
Totipotent
Pluripotent
Multipotent
Omnipotent
What is puberty?
developmental phase between childhood and adulthood whereby functional maturation of reproductive glands and external genitalia mediated by changes in sex hormones (GnRH, FSH, LH)
What are the two stages of Female Puberty?
Adrenarche (6-8) - adrenal production
Menarche (10-16)
Describe adrenarche.
Process of adrenal gland secreting androgens (DHEA) which is pre-programmed with an unknown trigger. This occurs at age 6-8 years. Androgens stimulate a growth spurt. Breast development begins.
Describe Menarche.
Onset of menstrual cycle occurring aged 10-16, to produce mature ova and endometrium to potentially support a fertilised cell (zygote). The HPO axis begins: GnRH (Hyp.) released binds to Anterior Pituitary which releases FSH and LH, travelling in the blood. LSH binds to theca cells to produce androgens and oestrogen.
Where is GnRH released from?
Hypothalamus
What does GnRH cause and where?
Release of FSH and LH from the Anterior Pituitary
Where does LH bind to in the female body? What effect does it exert?
Theca cells
Production of testosterone
Release of ovum (ovulation)
State 3 female phenotypic changes.
- Somatic growth
- Pubic hair
- Growth and maturation of reproductive tract
- Fat deposition: breast, buttocks, thighs
- Closure of epiphyseal plates: Stop growing
• Somatic growth occurs
At what age do males undergo puberty?
8-12 years old
Which cells to FSH bind to?
Sertoli
What effect does FSH have?
Spermatogenesis
What effect does LH have in males and where/
Binds Leydig cells to produce Testosterone
State 5 male phenotypic changes.
- Somatic growth
- Testicular enlargement
- Pubic hair growth
- Growth of larynx
- Deepening voice
Define fertilisation.
Process of male + female gametes fusing ≈ zygote
Sperm cells attach to which part of the ovum?
Corona radiata, entering the zona pellucida
What cellular change occurs to reduce further sperm entry?
1º block: Egg depolarises
2º block: Zona pellucida changes
Which reaction allows entry of sperm cell to the zona pellucida?
Capacitance then Acrosome reaction (exocytic reaction of enzymes)
Outline cleavage and compaction.
Process of conceptus held in fallopian tube and zygote undergoes successive divisions to become a morula (16-cell)
Outline blastocyst formation.
Process of 16-cell morula becoming a blastocyst at days 3-5.
Blastocyst has ICM (embryo) and trophoblasts (placenta)
What process allows the blastocyst into the uterus?
Progesterone levels rise, with SMC and conceptus goes into uterus
What does the blastocyst do to avoid immune rejection?
Secretion of immunosuppressive agents and ßhCG
Which organ maintains secretion of progesterone until the placenta takes over?
Corpus luteum
When detecting ßhCG, which cell produce this?
Syncytiotrophoblasts at day 7-8
Describe implantation.
Blastocyst adheres to endometrium wall via:
Embryo hatching - lytic factors from endometrial cavity digest zona pellucida
Apposition - contact between blastocyst and endometrium epithelium form a crypt of endometrium
Adhesion - trophoblast and uterine epithelium bind via microvilli of trophoblast
Invasion - syncytiotrophoblasts flow into endometrium in decidualisation
What is decidualisation?
Final stage of implantation whereby syncitiotrophoblasts flow into the endometrium causing oedema and vascularisation
Outline the formation of the placenta.
Syncytiotrophoblast cells erode through endometrial capillaries which bleed into space to give primitive placental circulation.
Cytotrophoblasts proliferate to produce primary chorionic villi. Mesenchyme from extramebryonic coelom invades to produce secondary. Finally mesenchymal cells form foetal capillaries to form tertiary chorionic villus.
How many layers are produced through decidualisation. State them.
3, giving a specialised endometrium of pregnancy
• Decidua basalis = underneath implanting embryo
• Decidua capsularis = overlies embryo
• Decidua parietalis = covers remainder of uterine surface
Outline the maternal and foetal blood at the placenta.
- 120 spiral arteries entering via uterus wall into intervillous space through pulsatile bursts
- Blood flow towards chorionic plate for adequate for exchange
- Blood drains through venous vessels in basal plate (no capillaries between arterioles and venules – placenta is essentially the capillary bed)
- 2 umbilical arteries (deoxygenated blood) -> branch beneath amnion -> penetrate chorionic plate + branch in chorionic villi to form capillary network
- 1 umbilical vein returns blood
Describe the blood-placental barrier in humans.
• Syncytiotrophoblasts regulate substance transport
State the main functions of the placenta.
- Endocrine: Steroids + Proteins
- Foetal lung: Gaseous exchange
- Foetal gut: Supplies nutrients
- Foetal kidney: Regulate fluid volume + Excretion
State the two main products of the placenta.
- ßhCG: Syncytiotrophoblast cells produce under direction of progesterone and oestrogens
- HCS1 + HCS2 (hPL): Polypeptide hormones related to GH and prolactin playing role in conversion of glucose to fatty acids and ketones + promote development of maternal mammary glands
Describe the effect foetal RBCs have on the O2 dissociation curve.
• HbF has 2 alpha and 2 gamma chains. Gamma chain has reduced 2,3-DPG affinity = higher O2 affinity -> dissociation curve shifts to left
Therefore at a lower ppO2, O2 saturation is higher
Describe how the following substances are transported across the placenta:
- Glucose
- Amino acids
- FAs
- Iron
GLUT1
AATs
FATP; pFABP
State 3 hormones the placenta produces
- hCG
- Oestrogens
- Progesterone
- hCS (hPL)
Which cells secrete hCG?
Syncytioblasts
Placenta (after 7 weeks)
What is the function of hCG?
• Prevent breakdown of corpus luteum at end of monthly female sexual cycle
By producing hCG, what do the syncytioblasts indirectly facilitate?
Production of hCG allows the maintenance of the corpus luteum which produces progesterone to prevent menstruation and help endometrium grow and store nutrients cf shed.
What are the functions of oestrogen generally?
- Enlargement of uterus
- Enlargement of breast ductal structure and growth
- Enlargement of female external genitalia
- Relax pelvic ligaments -> SI joint and pubic symphysis ≈ passage of foetus thorugh birth canal
How is oestrogen produced by the placenta?
Syncytioblasts do not produce oestrogen de novo. Adrenal glands produce DHEAS and 16-OH-DHEAS which is converted by trophoblasts into estradiol, estrone and estriol.
State the functions of progesterone.
- Development of decidua -> nutrition
- Reduced contractility of uterus ≈ reduce spontaneous abortion
- Conceptus development prior to implantation ≈ secretions and dilatation of fallopian tubes
- Aids oestrogen prepare breasts for lactation
Where is hCS produced?
• Protein hormone secreted by placenta at about 5th week of pregnancy
What is the highest amount of protein produced by the placenta?
hCS
What are the postulated functions of hCS?
• Partial development of breasts + lactation
During pregnancy, what is the output of the anterior pituitary like? State some hormones and which go up and which go down.
- Increased production of ACTH, TSH, PL
* Reduced production of FSH and LH
Which of the following go up or down during pregnancy:
- Glucocorticoids
- Aldosterone
- Thyroid hormone (T3/T4)
- PTH
- Relaxin
All increased
Which placental hormone increases thyroxine production?
hCG
Which hormone induces secretion of relaxin?
hCG
Which two effects does relaxin have?
Vasodilation
Ligament laxity
State which of the following metabolic and nutritional changes increase or decrease in pregnancy and how:
- Metabolism
- Nutrition
• BMR increases in latter half of pregnancy
- Require store prior to last 2 months of pregnancy when foetus requires however reserve required
- If not adequate reserve, nutritional deficiencies may occur: Ca, PO4, Fe, Vitamins DEAK
Describe the changes in maternal circulatory system in pregnancy.
- Blood flow through placenta + maternal cardiac output increased: Increased metabolism and blood flowing in maternal circulation increases cardiac output h/e falls in last 8 weeks of pregnancy
- Maternal blood volume increases during pregnancy: fluid retention (aldosterone + renal mechanisms) + hemopoiesis ≈ increased blood volume
- Maternal respiration increases during pregnancy: Increased oxygen requirement to meet increased BMR thus minute ventilation increases
What happens to maternal blood volume during pregnancy and why?
• Maternal blood volume increases during pregnancy: fluid retention (aldosterone + renal mechanisms) + hemopoiesis ≈ increased blood volume
What happens to maternal respiration during pregnancy and why?
• Maternal respiration increases during pregnancy: Increased oxygen requirement to meet increased BMR thus minute ventilation increases
Which three factors cause an increase in respiration rate during pregnancy?
Increased CO2 demands
Progesterone (sensitivity)
Foetus mechanical pressure upwards in abdominopelvic cavity
Outline the changes in kidney function during pregnancy?
Why is this?
• Urine output increased: Increased fluid intake + excretory
- Reabsorption increased: Sodium, chloride and water reabsorbed by steroid hormones of placenta and adrenal cortex
- Renal blood flow and GFR increased due to vasodilation (relaxin + progesterone)
Define Sex.
physical, biological appearance determined by anatomy, as a result of interactions of chromosomes and hormones
Does Sex equal Gender?
Sex ≠ Gender
State the two primitive duct systems all embryos have.
Wolffian (male) + Mullerian ducts (female)
In males, which primitive duct predominated?
Wolffian
In females, which primitive duct predominated?
Mullerian
Outline the process of male sex differentiation in utero.
Sex determining region of Y (SRY) chromosome codes testis determining factor (TDF) which causes differentiation of gonads to testes.
Testes secrete MIF and T which causes Wolffian ducts into reproductive tract whilst degenerating mullerian ducts.
Outline the process of female sex differentiation in utero.
No SRY chromosome thus no TDF which results in ovaries. No Testes production of T or MIF thus Mullerian ducts develop into female reproductive tract whilst degeneration of Wolffian ducts occurs
What is the standard EDD from last LMP?
40/40
Why may actual foetal age be EDD - 14 days?
• Ovulation will not be known thus actual foetal age can be EDD - 14 days (assuming 28 day cycle)
What is the week range for a delivery at term?
37-42
What is a pre-term birth?
< 37 weeks
What is a post-term birth?
> 42 weeks
Outline the trimester ranges.
1/3 = 0-12
2/3 = 13-27
3/3 = 28-40
When does organogenesis begin?
8 weeks - 12 weeks (1/3)
Outline processes which maintain the pregnancy state.
- Uterine quiescence: gap junctions downregulated + OTr downregulated + relaxin
- Anatomical arrangement of cervix: collagen fibres > smooth muscle + GAG ground substance (glue)
- Amnion + chorion membranes intact: Low level PG biosynthesis
State 3 processes which occur in preparation for parturition.
- Braxton-Hicks contractions (false labour)
- Cervical softening: PG + relaxin
- Relaxation of pelvic bones: Relaxin
- Foetus drops: Head is engaged with cervix
Outline the triggers for labour
- Oestrogen (drives CRH and ACTH and cortisol production)
- Oxytocin (sensitivity increased -> OTr)
- Cortisol (+ Pulmonary surfactant)
Which two hormones drive labour?
Oestrogen
Oxytocin
Outline the importance of cortisol in parturition.
Cortisol binds to foetal lungs increasing pulmonary surfactant protein in amniotic fluid which increases macrophages secreting IL-1ß.
The IL-1ß causes positive feedback to increase Our in the myometrium and increase responsiveness to OT
IL-1ß also causes increased PGE2 and cervical softening
Outline the importance of oestrogen in labour.
Oestrogen drives increased CRH then ACTH and cortisol and DHEA production.
Increased cortisol drives foetal lung maturation.
DHEA production increases oestrogen production (via chemical change), increases gap junction upregulation and increases Our in myometrium.
State the 3 stages of pregnancy.
1) Stage 1: Cervical dilatation: Latent + Active Phase
i) Latent Phase: Painful contractions + Cervical ripening + Dilation 3-4cm
ii) Active phase: Increased contractions + Descent + Cervical dilation (10cm)
2) Stage 2: Delivery of baby (Fully dilated cervix to Birth = 30-90 minutes)
3) Stage 3: Delivery of placenta and membranes (expulsion of placenta and membranes taking an hour)
Describe the Fergusson reflex.
What stage of labour does this occur in?
Uterine contractions push against the cervix which stimulates OT secretion from the Posterior Pituitary to increase OT and PGE2 which is positive feedback
Active stage of pregnancy - stage 1
What is postpartum involution?
shrinkage of uterus to pre-pregnancy size = 4-6 weeks
In the Fergusson reflex, which hormone secretion is being increased?
OT
In the non-pregnant state, why do breasts not fully develop milk production?
DA (PIH) dominates which inhibits PL release from the posterior pituitary
Outline the glandular structure of the breast.
Lobule bears alveoli which produce milk.
Alveoli produce milk and epithelial cells secrete into the lumen of alveoli. These are drained by a lactiferous due which converge at the lactiferous sinus onto the nipple.
The alveoli are surrounded by adipose tissue and supported by CT stroma and pectoral fascia
Describe the perfusion of the breast
Perfused by Internal Thoracic Artery, Lateral Thoracic Artery and Thoracoacromial branches
Describe the route of lymphatic drainage of the breast.
Axillary lymph nodes (anterior + lateral + posterior) to central to apical. From this, supraclavicular nodes drain into the subclavian and lymphatic trunk.
These drain into the R or L venous angle.
During pregnancy, what are the roles of the following hormones regarding breast development:
- Oestrogen
- Prolactin
- hCS
Oestrogen (duct development)
Progesterone (lobule formation)
hCS (enzymes for milk production)
Prolactin (synthesis of enzymes for milk production; milk production post-partum)
What two main processes are involved in lactation?
- Milk production
* Milk ejection reflex
Which two cell types are involved in milk production and ejection?
- Acini (Secretory alveoli)
* Contractile myo-epithelial cells
Outline the route of milk production in the breast.
Milk secreted by myoepithelial cells into lactiferous ducts which drain alveoli into lactiferous sinus and out via nipple.
Outline the suckling reflex.
Surge of prolactin due to suckling which travels afferently to posterior pituitary which stimulates OT (milk ejection) and PL (milk production)
Differentiate the difference in colostrum vs mature milk.
- Colostrum: Low calories, higher proteins, more fat-soluble vitamins (DEAK), more micronutrients Zn + Na, greater immunoglobulins (IgG and IgA)
- Mature milk (14-21 days): higher calories, higher carbohydrates, lower protein, lower in micronutrients, lower in immunoglobulins and lower in fat-soluble vitamins
What are the key differences between colostrum and mature milk?
Differ in:
- Calories (low colostrum)
- Protein (high colostrum)
- Micronutrients (colostrum higher in minerals)
- Vitamins (higher in colostrum)
- Immunoglobulins (IgG and IgA)
Which immunoglobulin is highest in breast milk?
IgA
Describe the process of weaning and its regime.
process of breastfeeding recommended for 6 months exclusively then continue with solid food until 2 years
List 5 risks of breastfeeding.
- Reduces infection risk
- Reduces SIDS risk
- Reduces childhood leukaemia risk
- Reduced T2DM
- Reduced obesity risk
- Reduced risk of breast Ca
- Reduced ovarian Ca
- Reduced OP
- Reduced CVD
- Economic
- Social
Define a foetal lie
longitudinal axis relation of foetus and uterus – usually longitudinal but may be transverse or oblique
Define the foetal position
Position: Relationship between denominator and mother’s pelvis
Define the presentation.
Portion of foetus felt on vaginal examination
Define the vertex of a foetus in pregnancy.
• Vertex: Area bounded by anterior fontanelle, posterior fontanelle and biparietal eminences
Define the occiput.
• Occiput: area below the posterior fontanelle
Define the sinciput.
• Sinciput: Area anterior to anterior fontanelle
Define labour.
onset of regular uterine activity associated with dilatation and effacement (thinning) of cervix and descent of presenting part through the cervix
Outline the 3 stages of pregnancy.
1) Onset of labour until cervix fully dilated (latent + established)
- Latent: Painful contractions where some cervical effacement and dilatation < 4cm
- Established: Painful contractions and cervical dilatation from 4cm
2) Cervical dilatation -> Head delivered
3) Delivery of head -> placenta and membranes
What is a Partogram?
Graphical display of intrapartum information assessing: power, passenger and passage
What are the 3Ps of a Partogram?
- Power: Freq. + Duration of Contractions
- Passenger: FHR + Position/ Station/ Moulding/ Caput
- Passage: Effacement + Dilation of Cervix
Give 3 indications for induction of labour and augmentation of labour.
- Prolonged pregnancy: 42/52
- Maternal DM
- Multiparity
- Pre-labour ROM
- SGA/IUGR/Placental insufficiency
- Hypertensive disorders
- Maternal medical disorders
- Maternal age
- Reduced foetal movements
- Maternal requests
What are the main forms of induction of labour?
Pharmacological: PGE2 or Syntocinon
Mechanical: Membrane sweep; Amniotomy; Balloon
State the form of administration of PGE2 in induction.
PV (Gel/Tablet/Pessary)
How does PGE2 analogues mediate the induction of labour?
Ripens the cervix and strengthens uterine contractions
What is the risk of administering PGE2 analogues in induction of labour.
Hyperstimulation
How does syntocinon mediate its effects in induction of labour?
Stimulate uterine contractions
State the form of administration of Syntocinon in induction.
IV infusion/dose titration to achieve contractions 4:10
Describe 2 forms of mechanical forms during induction of labour.
Membrane sweep
Amniotomy
Balloon dilation
Which adjunct is used for amniotomy?
Syntocinon
Which classification system is used in labour to check cervix progression?
Bishop’s Cervical Scoring System
What are the complications of induction of labour?
- Failure/repeat courses
- Uterine hyperstimulation (1-5%)
- Labour experience: examinations, discomfort, analgesic requirements, assisted vaginal deliveries (AVD)
- Increased obstetric intervention
- Uterine rupture
In the event of uterine hyperstimulation, what class of drugs may be given? Give an example.
Tocolytics
Terbutaline - ß2-agonist causing dilation
What is the general process of treating pain?
Prevent
Recognise
Assess
Treat
Outline non-pharmacological methods of pain relief in labour.
- Maternal support: 1:1 care in labour
- Birthing pools
- Other: Breathing + relaxation
Outline pharmacological methods of pain relief in labour
Entonox (O2:NO = 50:50)
Diamorphine (5-10mg)
Remifentanil
Epidural
Spinal block
General Anaesthetic
Which three forms of anaesthetic may be given in pregnancy.
Outline the benefits and drawbacks
Epidural (epidural space)
+ Efficacious cf parenteral opioids
+ Reversible with Naloxone
+ No increase in LUSCS (C/s?)
- Prolonged second stage: increase AVD
Spinal block (subarachnoid space) \+ Lasts longer cf epidural (2-4 hours) \+ Reversible with Naloxone
- Longer-lasting
General anaesthetic
+ ‘Complete pain relief’
- Higher risk: tissue oedema (more problems associated), reduced GI tone, increased IA pressure, delayed GI emptying (regurgitation and asphyxiation) + increased GI acidity (regurgitation)
Give 3 ways you may assess foetal wellbeing.
Pinard stethoscope
CTG
Foetal blood sample
State 3 factors determining FHR.
- Gestation: younger = faster
- Drugs: Impact rate and variability e.g. Mg = less variability
- Pyrexia
- Cerebral activity
- Hypoxia
- Cord compression
- Blood pressure
- Blood-gas concentration
What is a CTG?
investigation recording foetal heartbeat and uterine contractions during pregnancy
What systematic way is used to interpret a CTG?
Dr C BRAVADO
- Dr – Determine Risk:
- C – Contractions
- Bra – Baseline Rate -> 110-160bpm
- V – Variability -> 5-25bpm
- A – Accelerations
- D – Decelerations -> none or early + no concerning characteristics for 90 minutes
- O – Overall assessment
State 5 indications for continuous CTG monitoring in labour?
- Maternal tachycardia
- Maternal pyrexia
- Suspected chorioamnionitis/sepsis
- Presence of significant meconium
- Fresh vaginal bleeding
- Hypertension/Proteinuria
- Confirmed delay in labour (1st or 2nd stage)
- Hypertonus or tachysystole
- Oxytocin use
- Reported pain out-with the normal
- Preterm
- Multiple pregnancy
Outline how foetal blood sampling is conducted and why?
• Fetal scalp capillary sample -> assess acidaemia (pH > 7.25 = reassuring; pH < 7.20 = non-reassuring/immediate delivery)
What defines the foetal skull diameter?
Distance between occipitus and anterior fontanelle
During normal vaginal delivery, describe the movements the foetus makes accompanied by the pelvis in order to assist delivery.
- Pelvic inlet widest in transverse diameter -> often baby descends in L or R occipitolateral position
- Neck flexes so presenting diameter is suboccipitobregmatic (face)
- Internal rotation of head = occipitoanterior position
- Head delivers by extension + shoulders rotate into AP diameter of pelvis
- Anterior shoulder delivered by lateral flexion downward pressure on baby’s head
- Posterior shoulder delivered by lateral flexion upwards
What is malpresentation?
non-vertex presentation
Describe the various forms of malpresentation.
- Face
- Brow
- Breech (extended/flexed/footed)
- Transverse
Which three variations of breech presentation exist?
Extended - legs extended upwards
Flexed - legs flexed
Footed - feet are engaged
State the key indications for assisted vaginal delivery.
- Failure to progress into active 2nd stage of labour
- Maternal exhaustion
- Pathological CTG
- Abnormal FBS
- Prophylactic shortening of 2nd stage: hypertensive crisis/ cardiac disease/ cerebrovascular disease
Outline the criteria for assisted vaginal delivery.
- Consent
- Analgesia
- Empty bladder
- Abdominal palpation: head engaged 0/5 palpable
- Vaginal examination: cervix fully dilated (10cm), membranes rupture, presenting part at/below ischial spines
- Position of fetal head (OA/OP)
Note: If not OA, rehires rotational delivery via manual/ventouse/forceps
What are the two main forms of AVD?
Ventouse
Forceps
Evaluate the benefits and risks of the forms of assisted vaginal delivery.
Ventous
+ Less maternal injury risk
+ Less use of RA
+ Less post-op pain
- Less likely to result in successful vaginal delivery
- Cephalohaematoma (subperiosteal blood collection within suture lines)
- Subgaleal haematoma (subperiosteal blood collection crossing suture lines)
Forceps
+ Less likely to get intracranial injuries (cephalohaematoma/subgaleal haematoma)
+ higher % of successful vaginal delivery
+ Shorter time
- More likely to injure the mother - perineal and vulval tear
What is a complication of AVD?
State 2
Unintended consequence due to assisted vaginal delivery to either mother or baby
Shoulder dystocia
Subgaleal haematoma
Cephaloheamatoma
Facial palsy
Perineal tears
Describe a shoulder dystocia.
impaction of anterior shoulder behind symphysis pubis
State 3 RFs for shoulder dystocia.
- Macrosomia
- DM
- Post-term
- Obesity
- Multiparous
- AVD
- Prolonged 1st/2nd stage
State the potential foetal complications which may occur in shoulder dystocia.
- Hypoxia: trapped umbilical cord, pH drop, mortality (5-7% risk)
- Cerebral palsy
- Nerve damage: Excessive downward traction
A woman is experiencing a particularly challenging labour. There is a potential risk of a shoulder dystocia.
How would you manage this?
Management: HELPERR • Help • Episiotomy • Legs to McRoberts • Pressure • Enter manoeuvres • Remove posterior arm • Roll over
Outline the categories of perineal tear.
- 1st Degree: Injury to skin ± vaginal mucosa
- 2nd Degree: Injury to perineum involving muscles, not sphincter
- 3rd degree: Injury to perineum involving anal sphincter
- 4th Degree: Injury to perineum involving anal sphincter complex (EAS + IAS) + anorectal mucosa
How do you manage a perineal tear?
- Surgical management
* Physiotherapy
State 5 indications for a caesarean section.
- Malpresentation: Breech
- PMHx Cesarean
- Severe growth restriction/placental insufficiency
- Placenta praevia
- Suspected fetal compromise
- Failure to progress in labour
- Unsuccessful AVD
- Maternal request
- POH
- Twins
Outline the key categories for caesarean section need.
- 1: Requiring immediate delivery
- 2: Requiring urgent delivery
- 3: Requiring early delivery
- 4: Elective
Outline the process of a first breath.
Detachment from placenta causes a reduction in oxygen supply this hypercapnia and hypoxia drive to respiratory control centre in the Medulla. This drives the expansion of the lungs which is aided by a slight negative pressure (-25mmHg) present to oppose the foetal pulmonary surfactant.
State the causes of hypoxia during delivery.
Cord compression Placental abruption Premature placental separation Excessive uterine contraction Excessive anaesthesia
Which cells secrete pulmonary surfactant?
Type 2 pneumocytes
Which drug can be given to increase lung development in pre-term (<37 weeks) babies?
Steroids - bethametasone
State the main foetal variations in circulation.
Foramen ovale
Ductus arteriosus
Ductus venosus
What is the ductus venosus a conduit between?
Umbilical vein and IVC
What is the foramen ovale a conduit between?
RA and LA
What is the ductus arteriosus a conduit between?
Aorta and pulmonary artery
Outline how the foramen ovale is closed.
LA p > RA p due to ∆ in pulmonary resistance and systemic vascular resistance ≈ close septum over opening
Outline how the ductus arteriosus is closed.
• Closure of Ductus Arteriosus: Functional closure of ductus arteriosus as increased oxygenation of blood through ductus + PGE2 reduced (less vasodilation) + aortic pressure increases (due to systemic vascular resistance increasing) + venous pressure decreases (due to pulmonary pressure reducing) + fibrous tissue grows into lumen
Should the ductus arteriosus remain patent, what type of murmur is heard.
Continuous machinery murmur
How is a patent ductus arteriosus treated.
Indomethacin - NSAID thus reduces PGE2 to help close
Describe the changes in blood volume for the foetus after birth.
Isovolumic: Increased Hct but fluid lost into tissue space - increases with age
Describe the changes in CO in a newborn foetus.
High - 500mL/min
Describe the blood count differences between a foetus and an adult.
Higher WBC
Higher RBC (hypoxic stimulus) - stabilises at 4.75million/cm3 as drive reduced
Outline the key differences between a newborn foetus and an adult regarding ventilation.
Foetus RR = 40 cf adult RR = 12-16
Tidal air = 15mL
Minute ventilation = 640mL/min thus 2x cf adult
What is the risk of fluid and acid-base changes in a neonate and why?
• Acidosis and dehydration/overhydration %: Increased fluid intake and excretion + BMR high creating acid + incomplete kidney development
Why may jaundice be present in a newborn? Explain.
Physiological jaundice occurs due to bilirubin rising (from increase in erythrocytes) and inability of immature foetal liver to conjugate bilirubin with glucuronic acid thus physiological hyperbilirubinaemia.
Outline the process of Erythroblastosis foetalis.
How do you manage this?
Rh incompatibility occurs if baby inherits Rh positive RBC and mother is Rh negative. Mother detects foetal blood as foreign thus antibodies destroy foetal red blood cells and bilirubin is elevated in the neonate.
Manage with Anti-D
With an immature liver, which changes might you expect in a newborn infant?
- Hypoproteinaemia: Hepatic protein synthesis is low thus [plasma] reduces -> hypoproteinaemia
- Reduced glucose: Impaired gluconeogenesis function thus blood glucose level falls to half
- Reduced coagulation: Liver of neonate forms too little clotting factors
Describe the important thermoregulatory differences in the neonate.
BMR is high
Heat rapidly lost (high SA:V ratio)
Poor thermoregulatory mechanisms
High BAT - thermogenesis
Why may a neonate lose weight initially? Describe the processes involved.
Pre-partum, energy derived from glucose in maternal blood.
Post-partum, glucose supplied by immature liver and muscle glycogen. These stores are used up thus falling blood glucose.
Impaired gluconeogenesis due to immature liver thus catabolic process of lipolysis and proteinolysis to drive Kreb’s Cycle for ATP.
Weight loss occurs
Nutrients acquired from high-strength colostrum 2-3 days following
Which micronutrients are key yet difficult to absorb in the neonate?
Vitamin D - high requirement and poor GI absorption thus lower intake
Iron - depleted hepatic iron stores
Vitamin C - not stored well
What is the main form of immunity provided from the mother to the neonate in the 1st month?
Humoral immunity
Gamma globulins decrease
Alpha globulins present in breast milk
What age do gamma globulins begin to increase in the neonate?
12-20 months
State the key roles of microbiology.
- Diagnostic tests
- Interpretation of results + clinical consultations
- Treatment advice
- Infection control
Outline ways a microbiologist may make a diagnosis.
• Direct examination: Smear + Microscopy
• Culture: Culture diagnosis
• Serology: Agglutination + Precipitation + Complement fixation + Virus neutralisation
+ ELISA + RIA + Immunofluorescence
• Molecular: DNA hybridisation + PCR + LCR + Automated DNA amplification + Real time PCR
Weigh up the benefits and costs of direct examination vs microscopy.
Direct Examination • Smear diagnosis \+ Rapid \+ Simple \+ Cheap
- Not very sensitive
- Not very specific
- Requires expertise
• Microscopy
+ Variety of types
+ Quick
- Requires expertise
- May require preparation
Give 3 examples of specimens you can acquire.
- MSU
- Pus or swab wound
- CSF or blood
- Serology
- Sputum
- Lavage
Describe the difference between sensitivity and specificity.
- Sensitivity = ability to detect all of true positive (SnOUT)
- Specificity = ability to detect all true negatives (SpIN)
Describe what is meant by normal flora.
flora everywhere including commensal and opportunistic pathogens
