Female Pelvis and Fetal Skull Flashcards
What are the 4 bones that form the pelvis?
Sacrum, Coccyx and 2 coxal bones
What 3 things make up the pelvic space?
Pelvic brim, pelvic cavity and pelvic outlet
What makes up the true pelvis?
Pelvic cavity and pelvic outlet
What is the pelvic cavity?
from the brim to the outlet, following the curve of carus
What is the pelvic outlet?
the lower border of the symphysis, pubic arch, ischial spines and tuberosites, lower coccyx and sacrotuberous and sacrospinous ligaments
What are the three pelvic ligaments?
Anteroposterior, Oblique and transverse
What are the 4 types of pelvis?
Anthropoid, android, gynaecoid and platypelloid (flat)
Which pelvis is the most common?
Gynaecoid
What are the problems with classifying pelvis in this way?
- studied pelvis in a static way outside of labour
- pure models rarely happen it is more common top get mixed models
- each baby needs to adapt to each pelvis
What is the occiput?
The region lying between the foramen magnum and the posterior fontanelle
What is the vertex?
the area bound by posterior fontanelle, the two parietal eminences and anterior fontanelle
What is the Sinciput or brow?
it extends from the anterior fontanelle and coronal structure to orbital ridges
What is ossification?
the formation and hardening of fetal skull incomplete at birth.
What are sutures?
Small gaps left between the bones
What is a fontanelle?
When two or more sutures meet
What do we use to represent fetal position in clinical records?
the shape of the fontanelle and the sagital suture
What are the 5 stages of the birth mechanism?
engagement descent and flexion internal rotation extension extrernal rotation
What position will the fetal head normally begin labour in?
Asynclitism. The head is angled so that on of the parietal bones, rather than the vertex, presents at the pelvic inlet.
What happens after asynclitism?
The fetal heads descends through the pelvic inlet and then the head usually shifts into synclitism so that the vertex presents as the head descends further.
What is the pelvic floor made of?
muscle fibres and soft tissues suspended within the outlet of the pelvis forming a dome like sheet of tissue
What is the Levator ani muscle (LAM) made of?
muscle fibres and soft tissues suspended within the outlet of the pelvis forming a dome like sheet of tissue
What do the muscles of the Levator ani muscle do?
Maintain constant tone, except during voiding and defecation
Have the ability to contract quickly at times of acute stress like coughing and sneezing to maintain continence
Distend to allow the passage of the infant during childbirth and contract following to resume normal the function
What are the superficial pelvic floor muscles?
Ishiocavernosus
Bulbocavernosus muscle
Superficial transverse perineal muscle
Anal sphincter
What are the two types of pelvic movements?
extrinsic (pelvis as a whole) and intrinsic (pelvic bones with each other)
How are the pelvic joints held together?
by very strong ligaments that are designed not to allow movement
What gradually loosens the pelvic ligaments allowing slight pelvic movements?
the hormone relaxin
What is nutation?
opening the outlet
What is counter- nutation?
opening the inlet
What do women in 1st stage labour like?
they find relief in counter pressure on the lower part of the sacrum, which favours counter-nutation (opening the inlet)
What do women in 2nd stage labour like?
they tend to bend forward: the back muscles pull the coccyx and sacrum in nutation, opening the outlet
What does abduction mean?
knees apart
What does adduction mean?
knees together
