Week 1 - A - Anatomy 1 - Bony Pelvis Anatomy - Pelvic Fracture and Childbirth Flashcards
What bones does the bony pelvis consist of?
2 Hip bones
Sacrum and coccyx
What is the other name for the hip bones? What are the components of the hip bones?
Hip bones are also known as innominate bones (and are known as ossae coxae)
Hip bone - ilium, ischium and pubis
What are the main functions of the bony pelvis?
Transference of weight from the vertebral column (one column) to the femurs (right and left column)
Supports and protects the pelvic organs and the pelvic vessels
Passage for childbirths
Also support for when sitting and standing
What is the difference in the bones of the pelvic girdle and the bony pelvis?
Bony pelvis - 2 hip bones (ilium, ischium and pubis), sacrum and coccyx
Pelvic girdle - 2 hip bones (ilium, ischium and pubis), sacrum
Coccyx is not part of the pelvic girdle
Each hip bone is a fusion of the ilium, ischium and pubis Where do these three bones fuse to form and at what age?
The three bones fuse at to form the acetabulum (where the femur head inserts)
The fusion of three bones begins at puberty and should be completed by the age of 20 in males and females
Hyaline cartilage sits between the three bones forming the hip bone WHat is this cartilage sometimes known as?
This is known as the triradiate cartilage important when looking at an xray of a pediatric that there may be sutures on xray as the bone hasnt fused yet (not a fracture)
Where does the iliac crest run from? On the image state what the coloured arrows are pointing to
The iliac crest runs from the anterior superior iliac spine (ASIS) to posterior superior iliac spine (PSIS)
Green arrow - iliac crests
Dark red - PSIS
Bright red - Anterior inferior iliac spine
Black - ASIS
What is the notch lying slightly above the ischial spine in the ilium known as? What is the notch in the ischium lying just below the ischial spine known as?
Greater sciatic notch is a notch in the ilium lying just above the ischial spine
Lesser sciatic notch is a notch in the ischium lying just below the ischial spine
It is only when the bony pelvis is on it own with no ligaments that greater and lesser sciatic notch are under these names WHen ligaments lie over the notches, what are they known as? What are the ligamanets?
Sacrospinous and sacrotuberous ligaments
The sacrospinous ligament changes the greater scoatic notch into an opening, the greater sciatic foramen.
The sacrospinous and sacrotuberous ligaments change the lesser sciatic notch into an opening, the lesser sciatic foramen
What are the attachment points of the sacrotuberous and sacrospinous ligaments?
Sacrospinous - ischial spine to sacrum
Sacrotuberous - ischial tuberosity to sacrum
Which structures form the ischiopubic ramus?
Formed by the inferior pubic ramus and the ischial ramus
What nerve runs very close to the ischial spine? Where does and leave and re-enter the pelvic cavity? What does it innervate? Does it carry parasympatehtic or sympathetic fibres?
- The pudendal nerve runs very close to the ischial spine (Pudendal - S2,3,4)
- It leaves the pelvic cavity via lower part of the greater sciatic foramen to, passes over sacrospinous liigament very close to the ischial spine and re-enters via the lesser sciatic foramen
- Sympathetic fibres
What is the prominence on the ischium that can be felt when sitting down? What ligament attaches here?
This is the ischial tuberosity
The sacrotuberous ligament attaches here
What attaches between the ASIS and pubic tubercle? What connects the left and right pubic bones?
The inguinal ligament attaches between the ASIS and pubic tubercle
The pubic symphysis connects the left and right pubic bones
The pubic arch is formed by the convergence of the inferior rami of the ischium and pubis on either side What lies at the apex of the pubic arch?
The subpubic angle is the angle at which the ischiopubic rami on either side converge
The subpubic angle helps determine the sex of a skeleton How is this so?
In males the angle is typically less than 70 degress
In females the angle is typically more than 80-90 degrees
What bones do the bony pelvis consists of again? What forms the roof and lower boundary of the pelvic cavity?
Bony pelvis consists of the 2 hip bones, sacrum and coccyx
Roof of pelvic cavity - formed by the pelvic inlet
Lower boundary of pelvic cavity - formed by the pelvic floor
The pelvic inlet is more of a circle shape whereas the pevlic outlet is more oval shaped What course does the pelvic inlet run? What is another name for the pelvic inlet?
Runs from the sacral promontory, along the medial aspect of the ilium, along the superior pubic ramus and to the pubic symphysis where the course goes to the other side
The pelvic inlet is sometimes referred to as the pelvic brim
The pelvic outlet has the slightly more oval shape Describe the course of the pelvic outlet?
Runs from pubic arch, along the inferior pubic ramus inferiorly to the ischial tuberosity posteriorly and along the sacrotuberous ligaments to the coccyx (then continues back down sacrotuberous ligaments etc)
What is the largest muscle of the pelvic floor and what is its nerve supply?
The levator ani muscle - supplied by the pudendal nerve (S2,3,4)
What are the palpable surface landmarks of the bony pelvis? Which are felt on deeper palpation?
ASIS, most if not all of iliac crest, PSIS and ischial tuberosity should be palpable
Deeper palpation can feel coccyx, pubic tubercle and pubic symphysis
The pubic symphysis is an important anatomical landmark as it used in the measurement/estimation of the mother’s gestational weeks How does this work?
It is known as the Fundal Height
NICE GUIDELINES - Symphysis–fundal height should be measured and recorded at each antenatal appointment from 24 weeks
The superior apsect of the uterus is measured to the pubic symphysis - the lenght measured in centimetres correlates to the number of weeks pregnant that the mother should be
How is it possible to palpate the ischial spine? Which gender is it possible in?
The ischial spine is palpable in females
It is palpable on internal vaginal examination at approximately the 4 and 8 oclock positions - may be uncomfortable to palpate
It is only possible to palpate in females
The station of the fetal head is measured in centimetres above or below the ischial spines which is important for childbirth What else is the ischial spine a landmark for?
There a landmark for pudendal nerve - the pudendal nerve crosses behind the ischial spine before reentering the pelvic cavity via the lesser sciatic foramen
Important when considering pudendal nerve block
From the box in the top left, down and round to the box on the middle right- State what the bony features being pointed at are?
- Top left - Iliac crest
- Anterior superior iliac spine
- Ischiopubic ramus
- Pubic tubercle
- Superior pubic ramus
- Ischial tuberoisty (located posteriorly)
- Ischial spine
Name the structures being pointed to - from top left down and round to right
- Top left Sacroiliac joint
- Obturator foramen
- Pubic symphysis
- Hip joint - acetabulum and head of femur joint
What nerve passes through the obturator foramen and what does it supply?
Obturator nerve passes through the obturator foramen and supplies the muscles of the medial compartment of the thigh (and peripheral cutaneous innervation to medial upper thigh)
The ligaments of the pelvis assist in stabilisation of the pelvis When looking at the pelvis anteriorly, does the sacrospinous or sacrotuberous ligament sit more anteriorly?
Sacrospinous sits more anteriorly
Sacrotuberous sits more posteriorly - think that the sacrotuberous attaches to the ischial tuberosity which is very posterior
When the ligaments are in place, what do the greater and lesser sciatic notch become?
Greater sciatic notch becomes greater sciatic foramen
Lesser sciatic notch becomes lesser sciatic foramen
What direction to sacrospinous and sacrotuberous ligaments prevent the inferior part of the sacrum from moving and when? (thinking about when jumping or late pregnancy)
When there is sudden movement transferred through the vertebral column, the sacrospinous and sacrotuberous ligaments prevent the inferior part of the sacrum from moving posteriorly and superiorly ie jumping or late preganncy
The ligaments pelvis ie. sacrotuberous and sacrospinous relax during pregnancy Why is this and what hormone produced by the ovaries and placenta is this?
It allows the pelvis to move apart slightly to ease the delivery of the baby
The hormone is known as relaxin
What is the obturator foramen formed by?
The obturator foramen is formed by the ischium and pubis bones
The obturator membrane covers the obturator foramen What is the small gap located in the membrane for and what is it known as? Where is the small gap? What are the nerve roots of the obturator nerve? Obutrator internus lies over the obutrator membrane
The small gap in the obturator membrane is known as the obturator canal and allows the obutartor vessels to pass through
This obturator canal is found in the superior aspect of the membrane Nerve roots of the obturator nerve are L2,3,4
Trauma to the bony pelvis is not that common Bony pelvis is a ring structure Since it is a ring structure, what complications are likely to happen with a fracture?
If there is a fracture in one location of the bony pelvis, there is likely fracture in another location or a joint dislocation in another
What are some of the weak points of the bony pelvis which are more likely to fracture?
The pubic rami (superior and inferior)
The sacroiliac joints
The acetabulum
The ala of the ilium
Trauma to the bony pelvis can result in life threatening haemorrhage and/or damage to pelvic organs What pelvic organs can be damaged in trauma to the bony pelvis?
The bladder, rectum and uterus can be damage
Obviously just bladder and rectum in males
The sacral nerve plexus runs through the pelvic cavity and can be damaged What vessel coming off the abdominal aorta runs through the pelvic cavity?
The common iliac artery branches off the abdominal aorta to which the internal iliac artery enters the pelvic cavity and gives off branches supplying most of the pelvic cavity structures
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The picture on right of screen is female, the picture on the left is male Therefore the bony pelvis picture on the left would be worse for childbirth
Comparing the diameters of the male and female pelvis Whose AP (anterior posterior) diameter is bigger? Whose transverse diameter is bigger? Is this the case for both the pelvic inlet and outlet?
The AP and transverse diameter of the pelvis are greater in the female for both the pelvic inlet and outlet
The subpubic angle (and pubic arch) in female is wider than the male How can you use your fingers to demonstrate the size of the subpubic angle in males and females? What angle is the subpubic angle in males and females?
In males, upside down peace sign and the angle is the angle between the index and middle finger - angle is less than 70 degrees in male
IN females, angle between thumb and finger upside down - angle is greater than 80-90 degrees in female
The pelvic cavity is more shallow in the female- in the male is much deeper Bones are generally much thinner in female pelvis – more gracile and bones are much more robust in male WHat shape is the pelvic inlet said to be in males and females?
Pelvic inlet is said to be heart shaped in males
Pelvic inlet is said to be round shaped in females
What are the four fontanelles in a foetal skull? What is the colloquial term for the fontanelles?
The anterior fontanelle
The posterior fontanelle
The anterolateral (or sphenoidal) fontanelle
The posterolateral (or mastoid) fontanelle
Colloquial term for the fontanelles are the soft spot of the skull
The anterior and posterior fontanelles are the midline soft spots What bones does the anterior fontanelle sit between? Which of these bones fuse? When should the anterior fontanelle be closed by?
Anterior fontanelle is situated between the right and left parietal and frontal bones Frontal bones fuse which closes the anterior fontanelle Anterior fontanelle should be closed by 18 months after birth
Fontanelle is just a membrane covering the area of no bone – can tell a bit about hydration and nutrition of the baby What does the fontanelles look like in dehydration and malnutrition of the baby? What do they look like in raised intracranial pressure? What do they fontanelles allow for?
Fontanelles look shrunken when the baby is dehydrated or malnutritional state They fontanelles bulge when there is raised ICP The fontanelles allow for rapid stretching of the neurocranium as the brain grows faster than the surrounding skull can grow
What refers to the movement of one bone over another to allow the fetal head to pass through the pelvis during labour? The presence of the sutures and the fontanelles (“soft spots”) allows the bones to do this
Known as MOULDING and babies head should look normal again after a couple of days
Mastoid process usually only becomes properly bigger when the baby has head control and therefore which nerve passing though the stylomastoid foramen is less protected and can be compressed when using forceps to aid with childbirth ? What age does the baby have head control?
This would be the facial nerve - exits the skull via the stylomastoid foramen Baby develops head control at 3 months
What is the vertex of the foetal skull formed between?
It is a diamond shape between the anterior and posterior fontanelles and the parietal eminences
Is the foetal head longer than it is wide or vice versa? What are these diamters known as?
The foetal head is longer than it is wide Ie the occipitofrontal diameter is greater than the biparietal diameter - important in terms of childbirth
Is the transverse diameter of the pelvic inlet or AP diameter greater? IS the occipitofrontal diameter of the foetal head or the biparietal diameter wider? Therefore which way should the foetal head enter the pelvic cavtity through the pelvic inlet?
The transverse diameter of the pelvic inlet is greater than the AP diameter The occipitofrontal diameter of the foetal head is longer than the biparietal diameter Therefore the foetal ehad should enter the pelvic cavity with occiptofrontal diameter in line with transverse diamter - ie the baby facing right or left (means widest part of babies skull is at widest part of the pelvis)
The distance of the fetal head from the ischial spines is referred to as the station What does a negative and positive number mean when describing the station? How are the ischial spines felt on palpation of a female?
A negative number means the head is above the level of the ischial spines A positive number when describing the stations means the foetal head is below the level of the ischial spines The ischial spines are palpable on vaginal examination: approx. 4 and 8 o’clock positions
While descending through the pelvic cavity, the fetal head should be doing what?
The foetal head should rotate and the chin be flexed onto the chest
At the pelvic outlet, the AP diameter is wider than the transverse diameter Therefore what position should the foetal head be in? What position should the foetal ehad be in during delivery?
baby should ideally leave the pelvic cavity in an occipitoanterior (OA) position - hence the head rotation in pelvic cavity The foetal head should be in extension during delievery The occipital bone of the babies head should be at the anterior aspect of the mother
Describe the changes in the foetal head positions during labour
At the pelvic inlet - the foetal head should be in transverse direction (facing left or right) - this matches the widest area of the pelvic inlet (transverse diameter) with the widest part of he foetal head (occipitofrontal diameter) As the baby descends in the pelvic cavity the head should rotate and be flexed (chin on chest) At the pelvic outlet, the head should ideally lie occipitoanteriorly and extension of the enck should occur (occiptal bone of babies head at anterior aspect of mother)
Once baby’s head has delivered, there is a further rotation so that the shoulders and the rest of baby can then be delivered What is this position? it is the position used for childbirth supine position of the body with the legs separated, flexed, and supported in raised stirrups
This is the lithotomy position - position orignially used for removal of a calculus from kidney, bladder, or urinary tract
