Reproductive Physiology


Unit Overview: In this section you will learn about how each cell consists of 46 chromosomes. Also that women are XX and men are XY. Oxygen, wasts and neurtients are diffused during the pregnancy stage.Later on you will learn that the gonadotropic hormones have 3 primary effects on the gonads and what they are.

1. Sexual Reproduction- 20.1

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During sexual reproduction germ cells or gametes (sperm and ova) are formed in the gonads (testes and ovaries) during meiosis. During which the chromosomes split to create 2 gametes with 23 chromosomes each. When fertilization happens the sperm and ovum fuse together. This also joins the 2 gametes together again to create 46 chromosomes and creates a zygote (fertilized egg). As the zygote grows mitosis is happening over and over again to create a new life. After the baby hits puberty their gonads will be fully matured, the life cycle can start again.

Chromosomes
Each cell has 46 chromosomes. Which are 23 pairs of homologus chromosomes.

- Each of the homologus pairs excluding the 23rd pair (sex chromosomes) contain similar genes. You can see them here below in this picture.

- The first 22 pairs of chromosomes are called autosomal chromosomes.
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The zygote has 2 sets of autosomal chromosomes one from each parent. This means it also has 2 sets of genes which continues with the zygote as it goes through multiple stages of mitosis. Usually only one set of genes is active the other becomes silent. This process happens during the epigenetic changes to the chromatin by methylation of cytosine bases in DNA. This change will cause the genes to function differently in all the tissues of the body during the fetus development.Which will give the developing baby characteristics of both parents.
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The 23rd chromosome is also known as the sex chromosome

-In Females-XX, Males-XY
  • The X chromosome has 1,090 genes
  • The Y chromosome has only around 80 genes



Sperm that bear X chromosomes produce XX zygotes when they fertilize an ovum; sperm that bear Y chromosomes produce XY zygotes.

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  • Embryos that have the XY genotype develop testes; those without a Y chromosome produce ovaries.

  • The testes of a male embryo secrete testosterone and müllerian inhibitory factor. MIF causes degeneration of female accessory sex organs and testosterone promotes the formation of male accessory sex organs.
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The male accessory sex organs are the epididymis, ductus (vas) deferens, seminal vesicles, prostate, and ejaculatory duct.
  • The female accessory sex organs are the uterus and uterine (fallopian) tubes. They develop when testosterone and müllerian inhibitory factor are absent.
  • Testosterone indirectly (acting via conversion to dihydrotestosterone) promotes the formation of male external genitalia; female genitalia are formed when testosterone is absent.

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Numerous disorders of embryonic sexual development can be understood in terms of the normal physiology of the developmental processes.

Fertilization, Pregnancy, and Parturition




The sperm undergoes an acrosomal reaction, which allows it to penetrate the corona radiata and zona pellucida.
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  • Upon fertilization, the secondary oocyte completes meiotic division and produces a second polar body, which degenerates.

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  • The diploid zygote undergoes cleavage to form a morula and then a blastocyst.

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(A) the 4-cell stage

(B) cleavage at the 16-cell stage

(C) a morula formed from (B)

(D) a Blastocyst





Implantation of the blastocyst in the endometrium begins between the fifth and seventh day.

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This picture shows the process from Fertilization, cleavage, and the formation of a blastocyst.

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The trophoblast cells of the blastocyst secrete human chorionic gonadotropin (hCG), which functions in the manner of LH and maintains the motherís corpus luteum for the first 10 weeks of pregnancy.

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  • The trophoblast cells provide the fetal contribution to the placenta. The placenta is also formed from adjacent maternal tissue in the endometrium.
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  • Oxygen, nutrients, and wastes are exchanged by diffusion between the fetal and maternal blood.
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Amniocentesis shown in the picture to the right is a procedure of taking amniotic fluid containing suspended cells which are extracted to examine for any genetic deseases that could be forming.



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The circulation of blood in the placenta.
the mother's blood is delivered to the spaces between the chorionic villi in the placenta. the fetal blood is brought to the blood vessels within the villi from the umbilical cord.









The placenta secretes chorionic somatomammotropin (hCS), chorionic gonadotropin (hCG), and steroid hormones.

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  • The action of hCS is similar to that of prolactin and growth hormone. The action of hCG is similar to that of LH and TSH.
  • The major steroid hormones secreted by the placenta is estriol. The placenta and fetal glands cooperate in the production of steroid hormones.

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Contraction of the uterus in labor is stimulated by oxytocin from the posterior pituitary and by prostaglandins, produced within the uterus.
  • Androgens, primarily DHEA, secreted by the fetal adrenal cortex are converted into estrogen by the placenta.
  • Estrogen secreted by the placenta induces oxytocin synthesis; enhances uterine sensitivity to oxytocin, and promotes prostaglandin synthesis in the uterus. These events culminate in labor and delivery.
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The high levels of estrogen during pregnancy, acting synergistically with other hormones, stimulate growth and development of the mammary glands.

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  • Prolactin (and the prolactin-like effects of hCS) can stimulate the production of milk proteins. Prolactin secretion and action, however, are blocked during pregnancy by the high levels of estrogen secreted by the placenta.

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  • After delivery, when estrogen levels fall, prolactin stimulates milk production.
  • The milk-ejection reflex is a neuroendocrine reflex. The stimulus of suckling causes reflex secretion of oxytocin, which stimulates contractions of the lactiferous ducts and the ejection of milk from the nipple.
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2. Female Reproductive cycle

You have two ovaries that are suspended by ligaments from the pelvic girdle. They are halfway covered by uterine tubes. The uterus contains three layers. First is the outer most layer of connective tissue called the perimetrium, second layer is a smooth muscle calledthe myometrium, lastly you have the most inner layer consisting of epithelial called the endometrium. The endometrium consists of stratum functionale, which becomes thicker and then later sheds at menstruation.
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The vagina and urethra are both covered by longitudinal folds: the inner one is called the labia minora and the outer is called the labia majora. The ovaries consists of about 6-7 billion oogonia. As they make their way through apoptosis most of them die, but the ones that make it though are then called primary oocytes. Oogenesis stops at menopause. In response to FSH some oocytes will get larger as will the follicles which will then divide producing lots of layers of granulosa cells that will cover the oocyte and fill the follicle. If any primary follicles start to grow some more they are called the secondary follicles because they will have by then developed fluid filled cavities. One of these will go on to grow along with a fusion of its own vesicles to make a single fluid filled cavity. By this stage they are called the mature follicle. As the follicle developes it goes through its first meiotic division. The second meiotic division is only achieved if the oocyte was fertilized. Usually around the 10-14th day after the first day of menstruation the one follicle that has continued to grow is called the graafian follicle. Later the graafian makes a bulge on the surface of the ovary. With the right hormonal stimulation it will brake open starting the process of ovulation. The corpus luteum secretes both the estradiol and progesterone hormones.

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3. Endocrine Regulation of Reproduction
The gonadotropic hormones regulate the functions of the testes and ovaries and are secreted by the anterior pituitary. The gonads are stimulated by the gonadotropic hormones to secrete their sex steroid hormones. These steroid hormones have an inhibitor effect on the secretion of the gonadotropic hormones. During the first trimester of pregnancy, the embryonic testes are active endocrine glands that secrete high amounts of testosterone needed to masculinize the male embryo's external genitalia and accessory sex organs. The third trimester of pregnancy is when the ovaries mature. During the second trimester, testosterone secretion in the male fetus declines so that the gonads of both sexes are relatively inactive at the time of birth. The gonads secrete increased amounts of sex steroid hormones during puberty as a result of increased stimulation by gonadotropic hormones from the anterior pituitary.

The anterior pituitary produces and secretes two gonadotropic hormones: follicle-stimulating hormone (FSH) and luteinizing hormone (LH). The luteinizing hormone is sometimes called interstitial cell stimulating hormone (ICSH). The gonadotropic hormones have three primary effects on the gonads: (1) stimulation of spermatogenesis or oogenesis; (2) stimulation of gonadal hormonal secretion; (3) maintenance of the structure of gonads. LH and FSH is stimulated by a hormone produced by the hypothalamus and it is secreted into the hypothalamo-hypophyseal portal vessels.

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Pathway for the steroid hormones


Puberty
  • Triggered by the increased secretion of LH. Secretion of LH is pulsatile. Frequency and amplitude of the LH pulses increase at puberty.
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The pineal gland is located deep within the brain and secretes the hormone melatonin as a derivative of the amino acid tryptophan. Production of this hormone is influenced by light-dark cycles. Pineal glands of some vertebrates have photoreceptors. They are directly sensitive to environmental light. The secretion of melatonin increases at night and decreases during daylight. Pineal secretion is stimulated by postganglionic sympathetic neurons that originate in the superior cervical ganglion. Activity of these neurons is inhibited by nerve tracts that are activated by light striking the retina.

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Growth as a function of sex & age.







Other Sources to study and learn from.
PowerPoint,

Essential Questions:
-Describe the ovarian cycle and menstrual cycle. Describe what happens in each stage and the role of hormones. Include these terms in your description: follicular, ovulation, luteal, proliferation, secretory, menstrual, estradiol (estrogen), FSH, LH, GNRH, progesterone, follicle, corpus luteum, edometrium.

Ovarian Cycle: In response to FSH, some follicles enter the ovarian cycle and grow producing Granulosa cell layers while some primary follicles continue developing vesicles and becoming secondary follicles. As a follicle grows, the vesicles fuse to form a fluid-filled cavity. It is referred to as a graafian follicle. As a graafian follicle develops, primary oocyte completes Meiosis I. The second oocyte arrests at metaphase II. Between the oocyte and granulosa cells is a gelatinous layer that forms a barrier to sperm penetration. This is called zona pellucida.
Only one follicle survives after 10-14 days that menstruation begins. The rest are degenerative. Surviving graafian follicle forms a bulge on surface of ovary and secretes increasing levels of estrogen. Graafian follicle releases egg into fallopian tube at ovulation. If the egg becomes fertilized, oocyte completes meiosis II with formation of another polar body. Testosterone inhibits LH and GnRH secretion. LH causes empty follicles to become a corpus luteum that secretes progesterone and estrogen.

Uterine Cycle: a repeating series of changes in the structure of the endometrium; 21-35 days in healthy women of reproductive age; 3 phases:
  • Menses - Uterine cycle begins with the onset of menses. This is caused by the constriction of the spiral arteries which will reduce the blood flow to the endometrium. Secretory glands and other tissues begin to deteriorate. This is due to the lack of nutrients and oxygen. The weakened arterial walls rupture and blood pours into the connective tissues of the functional zone. Blood cells and degenerating tissues break away and enter the uterine lumen and travels to the vagina. This process is known as menstruation.

  • Proliferative - This is in the basilar parts of the uterine gland that survives menses. Days after menses has taken place, epithelial cells of these glands multiply and spread across the endometrial surface, restoring the integrity of the uterine epithelial. This phase is stimulated and sustained by estrogen. It is secreted by the developing ovarian follicles. By the time ovulation occurs, the functional zone is several millimeters thick. By this time, it is highly vascularized and has small arteries going to the myometrium.

  • Secretory - Endometrial glands enlarge and the arteries that supply the uterine wall elongate and spiral through the tissues of the functional zone. This occurs under the combined effect of progestins and estrogen from the corpus luteum. This phase begins at the time of ovulation and persists as long as the corpus luteum remains intact. After 12 days of ovulation, secretory activities peak. After that, the next couple of days the glandular activity declines and the uterine cycle comes to a close as the corpus luteum stops producing stimulatory hormones.
    • Mensus will start over again.


How does this apply to PTA:
This applies to us because if a patient is having cramps, they may not want to have traction applied to them because it might make it hurt more. Also if they are having their menstrual cycle, we might not be able to apply diathermy to them because it will make a heavier flow for the patient. With all the advancements in woman's health PT has a special type of PT for women who have vaginal issues or incontinence. With physical therapy women can learn how to do kegels which help them strengthen their pelvic floor. This is usually done for women suffering from incontinence after giving birth or because of aging. It can also help women who want to become pregnant or who have had difficult pregnancies to strengthen their pelvic floor muscle to make for a safer pregnancy and easier birth. Working the pelvic floor muscles can also be very helpful for men who also suffer from incontinence. This type of PT is more common with men who have had prostate cancer or surgery on their prostate and or bladder.



1. Fox, Stuart I. "Human Physiology." New York: McGraw-Hill, 2011. Print.
2. http://highered.mcgraw-hill.com/sites/0073378119/student_view0/chapter20/textbook_images.html
. http://www.iteachbio.com/Anatomy-Physiology/Reproductive%20System/femalereproductiveorgans.jpg