Tag Archives: lateral plate mesoderm

39. Bones, muscles and ligaments of the pelvis. The blood vessels and nerves of the pelvis. The bone tissue. Gastrulation, early differentiation of the intraembryonic mesoderm

9 Jan

39. Bones, muscles and ligaments of the pelvis. The blood vessels and nerves of the pelvis. The bone tissue. Gastrulation, early differentiation of the intraembryonic mesoderm

Flash Cards:

Bones of Pelvis

Bones of Pelvis

Bones of Pelvis 2 - sciatic foramens

Bones of Pelvis 2 - sciatic foramens

Blood Supply of Pelvis

Blood Supply of Pelvis

Blood Supply 2

Blood Supply 2

Nerve Supply of Penis

Nerve Supply of Penis

Autonomic Nerves of Pelvis

Autonomic Nerves of Pelvis

Anatomy: Bones, muscles and ligaments of the pelvis. The blood vessels and nerves of the pelvis.

Bones & Ligaments of Pelvis

Pelvis bony girdle
2 hip bones = ox coxae, = 3 bones fused together = ilium, ischium, pubis

Pelvic Diameters of female: important for birthing processes

  • Conjugate diameters – b/w symphysis and sacral promontory = 11cm
  • Tranverse diameters – mid point of brim on each side  = 13cm
  • Oblique diameters – iliopubic eminence –> sacroiliac joint = 17.5cm
  • To set axis correctly = ASIS +pubic tubercle in vertical line


Structures to show on pelvic girdle:

  1. Pubic symphyis
  2. Iliac crest
  3. Ant sup iliac spine (attachment of inguinal lig, plus part of way to find McBurney’s pt)
  4. Greater/Lesser sciatic forament
  5. sacral promontory
  6. ischio pubic rami
  7. inf pubic rami
  8. obturator foramen
  9. acetabulum
  10. ischial spine
  11. ischial tuberosities

Pelvic Girdle

Pelvic Girdle

Divided by pelvic brim:

false pelvis above = b/w iliac wings
true pelvis below = b/w pelvic brim and outlet

Pelvic brim = pelvic inlet


  • post = sacral promontory, massa lata of sacrum
  • lat/post =arcuate line of ilum
  • lat/ant = iliopubic eminence, then pectinate line
  • ant = pubic crest, pubic symphysis

Pelvic Outlet

  • ant = inf border of pubic symphysis, arcuate ligament, inf pubic rami (making subpubic angle)
  • lat = ischial tuberosities, sacrotuberous ligaments
  • closed off by pelvic and urogenital diaphragms

M of wall of true pelvis:
Show these on speciment of dried pelvis:

  • piriformis – triangular shaped m, can identify b/c the tendon will go to gr. trochanter of femur, and you will sciatic n emerge below it
  • ob internus m – can identify b/c only n. running to obturator foramen on the inside of pelvic cavity, will wrap around and cover the obturator foramen
  • pelvic diaphragm = coccygeus + levator ani m – point to muscles that attach to coccyx
  • UG diaphragm = deep transverse perineal m, fascia *may not be able to show this*

Differences b/w Male & Female Pelvis

  • Bones thinner, smaller, lighter in female
  • Inlet heart shaped in male, oval in female – in male, sacral promontory juts into to lesser pelvis
  • Outlet larger in female > male
  • Pelvic cavity wider/shallower in female
  • subpubic angle < 90 degrees in male, and obtuse in female (>90)
    • **Good one to tell difference, if asked if pelvis is male or female
    • If the subpubic angle is the distance as you making a peace sign with your fingers = male
    • if it is the same as the angle b/w you spreading your thumb/forefinger = female
  • female sacrum shorter and wider than male
  • obturator foramen is oval or triangular in female and round in male

Joints of Pelvis

  1. Lumbosacral joint b/w L5-sacrum, held by IV disk and supported by iliolumbar ligaments, iliolumbar a from int iliac a run next to this vertically
  2. Sacroiliac joint – synovial joint of plane type b/w articular cartilage of sacrum and ilium
    • ant/post sacroiliac ligaments
    • interossesus ligaments
    • transmit weight of body from vertebral column to pelvic girdle
  3. Sacrococcygeal joint – cartiliagenous joint b/w sacrum & coccyx
    • ant, post, lat sacrococygeus lig
  4. Pubic symphysis – fibrocartiliginous joint b.w pubic bones in medial plane, anteriorally

Major Ligaments of Pelvis
— good time to mention what goes thru gr/lsr sciatic foramen

  1. Sacrospinous – from sacrum –> ischial spine
  2. Sacrotuberous – from sacrum –> ischial tuberosities
  3. ant/post sacroiliac ligaments
  4. ant/post/lat sacrococcygeal lig
  5. ant longitudial lig – runs down front of vert bodies
  6. iliolumbar lig
  7. supraspinous lig

Pelvic ligaments ant view

Pelvic ligaments ant view

Greater Sciatic notch is split into 2 sciatic foramen via sacrospinous/ sacrotuberous ligament

Greater Sciatic foramen

  • Piriformis
  • sup/inf gluteal a/v/n
  • sciatic n * show this*
  • post femoral cut n
  • int pudendal a/v
  • pudendal n

NOTE – Piriformis m further separates the greater sciatic foramen into a supra/infrapiriformic hiatus.
The only structures that go thru suprapiriformic hiatus = sup gluteal a/v/n (Supra =superior)

Rest go thru infrapiriformic hiatus, as well as n to ob internus.

CLINICAL NOTE – Because of the emergence of these structures, anasthesia can only be given in the upper R quadrant of the gluteal region, so as not to paralyze any nerves, or harm blood supply

Lesser Sciatic Foramen

  • Ob internus
  • Int pudendal a/v
  • pudendal n

Remember: the pudendal structures come out of the greater sciatic foramen–> then turn around the ischial spine –> back in thru lesser sciatic foramen –> to Alcock’s canal running in the fascia over obturator int m in ischioanal fossa

Blood Supply of Pelvis

A. Int Iliac a – @ bifurcation of common iliac a, in front of sacroiliac joint, crossed in front by ureter @ pelvic brim

Post Division
: (3) = Iliolumbar a, Lat Sacral a, Sup Gluteal a
1. Iliolumbar a – sup/lat to iliac fossa, deep to psoas major, runs straight up, next to iliolumbar ligaments
Iliac br => iliacus m, ilium
Lumbar br => psoas major, quadratus lumborum

2. Lat sacral a – passes med, in front of sacral plexus, runs immediately to sacrum
spinal br (goes thru ant sacral formina) => spinal meninges, roots of sacral n, musc/skin overlying the sacrum

3.Sup gluteal a – b/w lumbosacral trunk + 1st sacral n
-leaves pelvis thru gr sciatic foramen above piriformis m
=> m. of buttocks

Ant Division (8) = Inf gluteal a, int pudendal, umbilical a, obturator, inf vesical, med rectal, uterine
1.Inf gluteal a – b/w 1&2 or 3&4 sacral n
leaves pelvis thru gr sciatic foramen, infrapiriformic hiatus

2. Int pudendal a – leaves pelvis thru gr sciatic foramen, b/w piriformis & coccygeis  –> perineum via lesser sciatic foramen

3. Umbilical a– v. tortous a, runs along lat pelvic wall & along the side of bladder
a) Prox part –> sup vesicle a => sup bladder
a of ductus deferens => DD, seminal vesicle, lower ureter, bladder

b)Distal part –> becomes obliterated, & goes forward as medial umbilical ligament

4. Obturator a
(can also come from inf epigastric a)
pass across femoral canal –> obturator foramen
ant br => m of thigh
post br => m of thigh
-acetabular br runs to acetabular notch –> head of femur via lig. capitum femoris

5.Inf vesical a (M, vaginal a in F) => prostate, fundus of bladder, DD, seminal vesicle, lower ureter

6.Vaginal a (F from uretine a/v or int iliac a)
numerous br => ant/post wall of vagina & makes logitudinal anatomosis  in med plane to make
ant/post azygos a of vagina

7.Middle rectal a
– run med => musc layer of lower rectum & upper anal canal, prostate gland, ureter (seminal vesicles, vagina)

8.Uterine a
(Deferential a in M) – from int iliac a or w/ vaginal or middle rectal a
run med in base of broad lig –> jxn of cervix & body of uterus & runs in front of /above ureter & near lat fornix of vagina
-sup br => body + fundus of uterus
-vaginal br => cervix + vagina

B. Median sacral a

unpaired a, arising from post aspect of abdominal aorta just before bifurcation
desc in front of sacrum => post rectum, end in coccygeal body as small vascular mass in front of tip of coccyx

C Sup rectal a
– from inf mesenteric a

D. Ovarian a – one of paired visceral branches of ab aorta,
crosses prox end of ext internal a –> minor pelvis + reaches ovary thru suspensory lig of ovary

Nerve Supply to Pelvis

A. Sacral Plexus
formed by L4-5 ventral rami (lumbosacral trunk) + 1st 4 sacral ventral rami, lies on piriformis m in pelvis, below pelvis fascia

1.Sup gluteal n (L4-5) – leaves pelvis thru gr sciatic foramen, suprapiriformic hiatus
=> gluteus medius,minimus, tensor fascia lata

2.Inf gluteal n (L5-S2)
– leaves pelvis thru gr. sciatic foramen => glut max m

3.Sciatic n (L4-S3) – largest n in body
a) Tibial n = post leg
b) Common fibular = ant/lat leg
deep/sup fibular branches
composed of peroneal & tibial parts
leaves pelvis thru gr sciatic foramen, infrapiriformic hiatus
runs thigh in hollow b/w ischial tuberosity & gr. trochanter

4.N to ob internus m (L5-S2)

leaves pelvis thru gr sciatic foramen, infrapiriformic hiatus
perineum thru lesser sciatic foramen
=> ob internus, sup gemellus m

5. N to quadratus femoris (L5-S1)
leaves pelvis thru gr sciatic foramen, infrapiriformic hiatus
runs deep to gemellus m, ob internus, and ends in deep surface of quadratus femoris
=> quadratus femoris & inf gemellus m

6. Post femoral cut n (S1-S3)

leaves pelvis thru gr sciatic foramen, infrapiriformic hiatus
lie w. sciatic n and desc on back of knee
inf cluneal n, perineal br

7. Pudendal n (S2-S4)

leaves pelvis thru gr sciatic foramen below piriformis –> perineum, thru lesser sciatic foramen => bulbospongiosus, ischiocavernosus, sphincter urethrae, deep/sup transverse perineal m

8. Br to pelvis

  • n to piriformis (S1-2)
  • n to levator ani + coccygeus m (S3-4)
  • n to sphincter ani
  • pelvic splanchnic n

*** Lumbosacral trunk connect sacral/lumbar plexus (L4-S4)



Histology: The bone tissue.

Embryology: Gastrulation, early differentiation of the intraembryonic mesoderm


  • makes the 3 defined germ layer of embryo = ectoderm, mesoderm, endoderm
  • @ day 21 = called trilaminar germ disk
  • indicated by primitive streak = epiblast cells
    • primtive groove, node, and pit
    • primitive node = cephalic end of streak, elevation around the primitive pit
  • caudal to primitive streak – future anus = cloacal membrane – epiblast/hypoblast fused here
  • epiblast = ectoderm + intraembryonic mesoderm + endoderm of trilaminar disk
  • @ wk 2 – intraembryonic mesoderm begins to form organs
  • @ wk 3 – extraembryonic mesoderm begins to form placenta

Differentiation to Intraembryonic Mesoderm

1. Paraxial mesoderm – right next to midline, become somites

  • first 7 = pharyngeal arches
  • 42-44 pairs of somites from rest of them –> eventually condense to 35 pairs
  • each somite has 3 parts: sclerotome, myotome, dermatome
    • sclerotome = bones, ligaments
    • myotome = muscle
    • dermatome = skin

2. Intermediate Mesoderm – b/w paraxial and lateral mesoderm

  • forms urogenital ridge –> kidney & gonads

3. Lateral Mesoderm

  • intraembryonic coelem forms – splits lat mesoderm into 2 layers
    • somatic
    • visceral

4. Notochord – mesoderm in midline from primitive node –> prechordal plate

  • stimulates ectoderm on top –> neuroectoderm –> neural plate
  • stimulates formation of vertebral bodies & nucleus palposus

5. Cardiogenic region

  • horseshoe shaped region of mesoderm  @ cranial end of embryonic disk
  • is the future heart