Labour And Birth

Question 0

Estrogen in initiation of labour

Answer 0

• Promote gap junctions formation in myometrium
• increase oxytocin receptors and their sensitivity
• increase prostaglandin synthesis
• softening of Cx

Question 1

3 mechanisms of initiating labour

Answer 1

Estrogens
Oxytocin
Prostaglandins

Question 2

Oxytocin in initiation of labour

Answer 2

• Increases myometrial contractivity & frequency of pacemaker APs through fergusons reflex
• lowers AP threshold and mediates prostaglandin synthesis

Question 3

Prostaglandin role in initiation of labour

Answer 3

Increase gap junction, intracellular Ca++ & frequency of APs

Enhances cervical softening

Question 4

First stage of labour: definition

Answer 4

Begins: onset of regular contractions
Ends: full dilation of Cx

Question 5

First stage of labour: uttering contractions

Answer 5

Coordinated by pacemaker cells
Fundal dominance
Myometrial cells exhibit retraction (greatest in fundus)
Contractions decrease uterine cavity, pushing presenting part to Cx

Question 6

First stage of labour: Cx

Answer 6

Effacement: thinning and merging of upper Cx with lower uterine segment
Dilation: opening of the external Cx so to width of presenting part, aprox 10cm

Question 7

Second stage of labour

Answer 7

Begins: full dilation
Ends: birth of baby

Question 8

Mechanism of labour:

Answer 8

Descent 
Flexion 
Internal rotation
Crowining and Extension
Restitution
External rotation of head/ internal rotation of shoulders
Lateral flexion

Question 9

Third stage of labour:

Answer 9

Begins: birth of baby
Ends: birth of placenta and membranes

Question 10

Third stage: placental separation

Answer 10

• delivering contraction reduces placental site causing placenta to buckle
• intervillous blood forced back in to decidua causing congestion in chorionic capillaries
• chorionic vessels begin to rupture and pull on decidua causing separation within decidua

Question 11

Third stage: physiological control of blood loss

Answer 11

• living ligatures
• uterine walls pressure
• hypercoagulability, clot formation begins during separation

Question 12

Labour physiology: CV system

Answer 12

• CO & BP progressively rise, significant increases during contractions
• increased erythropoises and coagulability

Question 13

Labour physiology: respiratory

Answer 13

RR, tidal volume and ventilation all increase to accommodate increased O2 demand

Question 14

Labour physiology: renal, body fluid and temperature

Answer 14

Increases renin-angiotensin activity, blood volume, osmolarity and body temperature

Question 15

Labour physiology: GI and metabolism

Answer 15

• overall decreased GI activity

- increased metabolic needs met by increased glucose use and lipolysis

Question 16

Types of nociceptors in the body

Answer 16

Mechanical
Thermal
Chemical
Polymodal

Question 17

Location of nociceptors in the body

Answer 17

Cutaneous
Viscera
Somatic

Question 18

Pathway for pain:

Answer 18

Primary sensory neuron > secondary sensory neuron > tertiary sensory neuron

Question 19

Primary sensory neurons are

Answer 19

• Connected to nociceptors
• run to dorsal horn of spinal cord
• 2 types:
  
  • alpha-delta fibres (myelinated)
  • c fibres (unmeylinated)

Question 20

Secondary sensory neurons are…

Answer 20

Decussates (crosses over) immediately

Ascends within spinothalamic tract to thalamus

Question 21

Tertiary sensory neurons…

Answer 21

Thalamus > primary somatosensory cortex (conscious perception of pain) AND lambic system (emotional response to pain)

Question 22

Referred pain

Answer 22

Visceral pain sensed in somatic areas:
Visceral sensory pain pathways run within the same tract as somatic sensory pathways and the brain cannot distinguish between the two.

Question 23

Pain perception occurs when:

Answer 23

Action potentials are received by the primary somatosensory cortex

Question 24

What does the primary somatosensory cortex determine:

Answer 24

Location and Intensity of pain

Question 25

Prefrontal cortex and lambic system

Answer 25

PFC: behavioural response
Limbic: emotional response

Question 26

Paint tolerance v. Pain threshold

Answer 26

Tolerance: subjective perception of pain
Threshold: intensity of stimuli to generate AP in nociceptive neuron

Question 27

Physiological mechanisms for pain regulation

Answer 27

Afferent
Descending
Endorphins

Question 28

How does Afferent pain regulation work?

Answer 28

Simultaneous activity of lower threshold stimulate non-nociceptors mechanoreceptors of alpha-beta primary sensory neurons > also synapse with secondary sensory neurons in pain pathway causing hyperpolarisation > reduces the pain signals received by the thalamus

Question 29

Descending regulation

Answer 29

• Ability of brain to diminish/suppress the pain sensation
• periaqueductal grey matter (PAG) is a group of neurons in the midbrain:
  Receives pain signals from brain regions > sends AP to dorsal horn of spinal cord to depress activity of nociceptors as it enters the spinal cord

Question 30

Endorphins

Answer 30

Endorphins are peptides (small proteins) that bind to opioid receptors
Located in CNS to process/modulate nociceptor information

Suppress release of neurotransmitters
Hyperpolarise the cell membrane of neurons in pain pathway

Question 31

Locations of Pain in labour

Answer 31

Viscera : uterus, Cx blood vessels
Somatic: pelvis, vagina, perineum
Cutaneous: skin of perineum

Question 32

Trauma that can occur during vaginal birth

Answer 32

Bruising
Swelling
Stretching
Tearing
Placental separation

Question 33

Perineal tears

Answer 33

1st: fourchette only
2nd: fourchette, and muscles of perineal body
3rd: fourchette, perineal body and external anal sphincter
4th: 3rd + internal anal sphincter and anal mucosa

Question 34

Trauma in cesarean section

Answer 34

Laceration of skin, connective tissue and skeletal muscle and smooth muscle
Placental separation