Pharmacology of the Uterus

Question 1

Briefly describe the muscular structure of the uterus

Answer 1

• outer longitudinal fibres
• middle figure-eigth fibres
• inner circular fibres

Question 2

What are some mechanical properties of the myometrium?

Answer 2

• contractions mean increasing in uterine pressure forcing content towards cervix and acts as a natural ligature to prevent blood loss
• spontaneously active (myogenic) - produces regular contractions without neural or hormonal input
• highly sensitive to neurotransmitter and hormones
• rhythmic contractions for parturition

Question 3

What factors initiate uterine contractions?

Answer 3

1. Spontaneous depolarisation of ‘pacemaker’ cells called ICCs
2. Electrical communication between cells (ICCs, smooth muscle cells)
3. Gap junctions spread depolarisation
4. Myometrium can function as a syncytium - allows whole organ to work together as one functional unit

Question 4

Main reason for uterine contractions occuring:

Answer 4

1.Basal and elevated [Ca2+] - works similar to other smooth muscle tissues

2.[Ca2+]i&raquo_space;»»»» contraction
- VGCC open
- Ca2+ influx
- Depolarisation spreads through pacemaker cells
- Depolarisation initiates contraction

3.Graded response: incremental increases in [Ca2+]i&raquo_space;»» incremental increases in force of contraction}}