Caffeine is a natural stimulant
Uncommon Infant and Newborn Problems. Promotes growth in children; prevents anemia by regenerating red blood cells; aids in the metabolism of carbohydrates, fats, and proteins; maintains healthy nervous system. Selenium toxicity causes nervous system changes, fatigue, and irritability. Caffeine's potential health benefits As well as its stimulating effects, caffeine has been heralded for providing an array of health benefits. Protein intake and intake of individual amino acids can affect brain functioning and mental health. Dysuria see Urine and Urination.
Incredibly, hormones direct the ovarian end of the uterine tubes to draw close to the ovary in time for ovulation, 20 and cause the number and types of cells lining the uterine tube and uterus to change cyclically. Each uterine tube measures about 10 to 13 centimeters in length 21 and has an inside diameter between 22 1 and 2 millimeters. As shown in Figure 0. The uterine tubes are lined with several cell types, one of which has small projections, called cilia, which work to direct the oocyte or embryo down the uterine tube toward the uterus.
The wall of each uterine tube contains two muscle layers which contract in rhythmic fashion to further direct transport of the oocyte, or in the case of fertilization, the embryo, toward and into the uterus. The uterus is a small, muscular structure which, in the event of pregnancy, serves to house, nourish, and protect the embryo and fetus until birth and then expel the fetus during childbirth.
For example, the adult uterus prior to a first pregnancy measures about 6 to 8 centimeters in length and weighs about 70 grams. By the end of full-term pregnancy, the uterus weighs approximately grams and displaces a volume of about five liters. The uterus is divided into distinct regions Fig. The upper corners of the uterus where the uterine tubes enter are called the cornu.
The upper two thirds of the uterus is called the body and the uppermost part of the body between the insertion sites of both tubes is called the fundus. The cervix refers to the lower third of the uterus and is separated from the body by a narrowing called the isthmus. Within the cervix lies the cervical canal which has an upper, internal opening called the internal os and a lower opening into the vagina called the external os. The wall of the uterus contains 3 distinct sections called the endometrium , myometrium , and perimetrium.
The endometrium forms the inner lining of the uterus and undergoes dramatic cyclical changes as part of the menstrual cycle. Its thickness varies from about. The myometrium is the middle layer of the uterine wall and is composed of smooth muscle and connective tissue.
The myometrium is 12 to 15 millimeters thick, 30 makes up the vast majority of the uterine wall, and expands greatly during pregnancy. The muscle component is most prominent in the body of the uterus and least prominent near the cervix. The perimetrium is the thin outer covering of the uterus 32 and is not of particular interest in this discussion.
The vagina receives the male reproductive cells and serves as the birth canal through which the fetus passes during childbirth. The process of forming female reproductive cells, called oocytes, is called oogenesis. Female reproductive cells form in the ovaries, which contain four important cell types called oocytes , follicular cells, granulosa cells, and theca cells.
Each oocyte and its surrounding cells form a functional unit called a follicle. The type, size, structure, and complexity of follicles will be further described below. Primary germ cells are the source of oocytes. In the human embryo, about to primary germ cells 34 travel to the developing ovaries from the yolk sac See UNIT 5 during the 5th week of embryonic development.
Between 3 and 4 months, the oogonia begin to enlarge and start their first meiotic division and are called primary oocytes. By birth, only 2 million are present. During the fetal period, each primary oocyte achieves a diameter of 20 micrometers and is surrounded by a single layer of flat epithelial cells called follicular cells.
Little change occurs in these follicles until puberty when the menstrual cycles begin as described below. The pituitary gland is located just underneath the brain and produces a total of 8 hormones which control numerous vital functions of the human body.
As each menstrual cycle begins, FSH and LH activate between 6 and 20 primordial follicles to begin a rapid growth phase. An acellular material called the zona pellucida forms between the oocyte and the granulosa cells. The cells surrounding the oocyte are now called granulosa cells and the cells surrounding the granulosa cells are called theca cells. The primary oocyte now has a diameter of 50 to 80 micrometers.
During this process, granulosa cells and theca cells gain the ability to produce a hormone called estrogen. During this process, these antral follicles including the oocyte within grow substantially in size adjacent to the antrum and are sometimes called vesicular follicles 53 Fig.
By about 1 week into the cycle, 1 of the follicles distinguishes itself by growing the fastest and the others begin to shrink. Nonidentical twins occur when 2 follicles release their oocytes nearly simultaneously and both become fertilized and implanted. Ovulation is preceded by a 6- to fold increase in LH levels, a 2- to 3-fold increase in FSH, a fall in estrogen levels, and a rise in progesterone levels Figure coming soon. Note that without the LH peak about 16 hours prior to ovulation - some authorities report the LH surge precedes ovulation by up to 36 hours , ovulation will not occur.
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