Biology 120 ww5Medical Terminology

Chapter 10

Reproductive system

Jennifer Stevenson

The inner lining of the uterus is called the endometrium.

The function of the endometrium as a lining of the uterus to be an implantation site for a blastocyte upon its arrival to the uterus. By that time, the endometrium is a thick, blood vessel rich tissue layer.

During pregnancy, the glands and blood vessels increase in number and size which then forms the placenta that supplies the baby with nutrients and oxygen.

It consists of a single layer of columnar epithelium, resting on a layer of connective tissue, which varies in thickness according to hormonal influences - the stroma.

Menstruation

The endometrial lining undergoes cyclic regeneration It initially proliferates under the influence of estrogen. However,

once ovulation occurs, in addition to estrogen, the ovary will also start to produce progesterone.

If the blastocycte does not implant and provide feedback to the body with human cortico goandotropin and continued feedback through pregnancy with placental progesterone and estrogen, the endometrial lining is either reabsorbed (estrous cycle) or shed (menstrual cycle).

The process of shedding involves the breaking down of the lining, the tearing of small connective blood vessels, and the loss of the tissue and blood that had constituted it through the vagina. The entire process occurs over a period of several days. Menstruation may be accompanied by a series of uterine contractions; These help expel the menstrual endometrium.

Pregnancy

In case of implantation, it remains as decidua which becomes part of the placenta; it provides support and protection for the gestation.

The glands and blood vessels in the endometrium further increase in size and number. Vascular spaces fuse and become interconnected, forming the placenta, which supplies oxygen and nutrition to the embryo and fetus.

The organ in which the developing fetus resides in is called the uterus.

The Uterus

The uterus (also know as the womb) is a hollow, pear-shaped organ with a thick muscular wall, a mucous membrane lining, and a rich supply of blood. It is located in a woman's lower abdomen between the bladder and the rectum.

The narrow, lower portion of the uterus is the cervix; the broader, upper part is the corpus. The corpus is made up of two layers of tissue.

The endometrial lining of the uterus that contains a rich blood supply, reacts to hormonal changes that prepare it to receive a fertilized ovum that plants itself into the endometrial wall. It provides nutrients and protection for the baby.

The uterus during pregnancy During pregnancy the uterus grows upwards out of the woman's pelvis.

The top of the uterus (or fundus) can be felt by your caregiver feeling your belly after about 12 weeks of pregnancy. By 24 weeks of pregnancy, the myometrium muscles start stretching upwards, forming the thicker upper segment of the uterus. This leaves a thinner layer of muscle below it, known as the lower segment. The lower segment separates the cervix from the upper segment and has the role of 'taking up' or absorbing the cervix as it dilates during labor.

The muscles in the lower segment encircle the lower third of the uterus and is a relatively weaker layer of muscle with less blood supply, compared to the upper segment. This is why the cut to perform a Caesarean operation is done in the lower segment (across the top of the pubic hairline), where it is less likely to cause excessive bleeding.

The uterus has a natural tendency to lean slightly towards the woman's right side during later pregnancy, but is held in place by ligaments. These ligaments stretch as the uterus grows, acting like supportive anchors to stabilize it, while facilitating the baby's movements within.

The time required for the

development of a fetus is called

gestation.

Gestation The carrying of an embryo or fetus inside a female animal. Pregnancy can be divided into three trimesters, each three

months long. The first trimester is from the last period to the 13th week, the second trimester is from the 14th to 27th week, and the third trimester is from the 28th week through the 40th week.

Birth normally occurs at a gestational age of about 40 weeks, though a normal range is from 37 to 42 weeks which is 9 months and 1 week. Childbirth occurring before 37 weeks of gestation is considered preterm, (premature) whereas childbirth after 42 weeks is considered post term (late). Preterm and low birth weight babies make up the second leading cause of infant death at about 17%. Preterm births solely consist of 12% of infant deaths with an 84% majority within the 32–36 week period. It is estimated that two million babies worldwide die annually within 24 hours of birth.