Uterus (Embryolog-Anatomy-Histology)

Uterus embryological development

* It arises from Mullerian duct.

Uterus description

Site:in the pelvis between urinary bladder anteriorly & rectum posteriorly.
Size:
· Dimensions:
In nullipara : 1 × 2 × 3 inches.
In multipara : 1.5 × 2.5 × 3.5 inches.
· Ratio between corpus & cervix:

Shape:pyriform.
Weight :
Nullipara : 50 gm.
Multipara : 75 gm.
Supports:
1) Cervical ligaments.
2) Ligaments of body.
3) Anteversion of uterus.
Parts:
1)Uterine body (corpus):
· Forms the main bulk of uterus.
· Fundus: above the level of uterine tubes.
· Cornu: * area of insertion of each fallopian tube.
* attached to it:
1. Fallopian tube: centrally.
2. Round ligament: anteriorly.
3. Ovarian ligament: posteriorly.
2)Isthmus: (5 mm)
· Situated between cervix & body.
· Extends from the anatomical internal os above, to the histological internal os below.
· Lined by modified endometrium (?).
· Expands during pregnancy forming LUS during last trimester.
· Hormonal effect?!!!!!
3) Cervix: (2.5 cm)
· Elongated lower most part of uterus.
· Demarcated from the body by the isthmus.
· 2 parts: *supravaginal part.
*vaginal part (portiovaginalis).
· Cervical canal is spindle-shaped.
· Upper opening is internal os.
· Lower opening is external os: *pin hole in nullipara.
*slit in multipara.
Position:with empty bladder anteverted anteflexed:
· Anteverted: the cervix nearly at right angle with the vagina.
· Anteflexed: the uterus is bent forwards on the cervix making an angle about 160.
· This position is maintained by:
A. Rapid growth of posterior uterine wall > anterior uterine wall.
B.Weight of intestine & ↑intra-abdominal pressure pushing body downwards.
C. Round ligaments pull the fundus forwards.
D.Tone in uterosacral ligament pulls cervix backwards.
[B]N.B.: in 15% of normal women, RVF is present.
Peritoneal covering:
·Posteriorly: completely covered by peritoneum.
·Anteriorly: covered with peritoneum except anterior surface of cervix.
·On both sides: peritoneum forms the broad ligament.

Uterus relations:

i. Of the body:
· Anteriorly: UB and vesico-uterine pouch.
· Posteriorly: Douglas pouch with loops of intestine.
· Laterally: broad ligament & uterine vessels.
ii. Of the supravaginal portion of cervix:
· Anteriorly: Urinary bladder located in front.
· Posteriorly: It is anterior wall of Douglas pouch.
· Laterally: ½ inch lateral to internal os crossing of uterine artery above ureter.

Uterus structure (Histology):

A) Histology of body(3 layers):
1) Endometrium:
· Endometrial tubular glands formed of single layer of columnar epithelium.
· Under effect of steroids ,this layer is differentiated into:
i. Superficial compact layer sheds with menses.
ii. Middle spongy layer sheds with menses.
iii. Basal compact layer: regenerates again.
· Endometrial thickness varies according to phases of menstrual cycle from 1-8 mm.
2) Myometrium: arranged into 3 layers:
· Outer longitudinal layer.
· Middle interlacing fibers: in criss-cross fashion forms figure 8 around blood
vessels leading to controls bleeding during menses & 3rd
stage of labour, so called living ligature.
· Inner circular.
3) Peritoneal coat:
· Peritoneum covers the body of uterus:
· Anteriorly: reflected on the UB to form utero-vesical pouch.
· Posteriorly: reflected on the rectum to form Douglas pouch (Cul de sac).
· Peritoneum covers supravaginal portion of cervix.
· The serous coat is firmly adherent to subserous layer except laterally to
form broad ligament.
B) Histology of the cervix(3 layers):
1) Endocervix:
· Lined by simple columnar epithelium.
· Thrown into folds, so called compound racemose glands.
· Secretes alkaline cervical mucus.
· Liable to chronic infection (WHY?!!!!!).
2)Muscle layer:outer longitudinal & inner circular.
3) Ectocervix:covered by stratified squamous epithelium.

Uterus blood supply

A) Arterial :
I. Uterine artery:
Arises from the anterior division of internal iliac artery.
It supplies most of the uterus.
II. Ovarian artery:
Branch from aorta at level of L2.
It supplies the fundus uteri.
B) Venous:
Starts as pampiniform venous plexus between the 2 layers of broad ligament:
– Uterine vein: drains into internal iliac vein.
– Ovarian vein: *Right ovarian vein: drains into IVC directly.
*Left ovarian vein: drains into left renal vein which drains into IVC.

Uterus nerve supply

Via branches of inferior hypogastric plexus
– Uterus is sensitive to distension (stretch).
– Cervix is sensitive to dilatation (stretch).
– Both are insensitive to touch, cutting & burning.

Uterus lymphatic drainage

1. Fundus:Para-aortic lymph nodes via ovarian lymphatics.
2. Cornu:superficial inguinal L.Ns within inguinal canal via lymphatics of round ligament.
3. Body:internal iliac L.Ns then external iliac L.Ns via uterine blood vessels.
4. Isthmus:has the same drainage as cervix.
5. Cervix:
A. Primary group:
· Paracervical & parametrial L.Ns.
· Obturator, internal iliac & external iliac L.Ns.
B. Secondary group:
· Lateral sacral L.Ns.
· Common iliac L.Ns.

Uterus (Embryolog-Anatomy-Histology) videos

Uterus – Anatomy, Definition and Function – Human Anatomy | Kenhub video

https://www.youtube.com/watch?v=LUtjft-8s5k

Uterus by Dr. Fabian video

Uterus (Embryolog-Anatomy-Histology) power point presentations:

Anatomy of female genital tract

Anatomy of female reproductive organs