Podcast
Questions and Answers
What is the primary function of fructose in the seminal fluid produced by the seminal vesicles?
What is the primary function of fructose in the seminal fluid produced by the seminal vesicles?
Which of the following best describes the secretion produced by the prostate gland?
Which of the following best describes the secretion produced by the prostate gland?
What role do prostaglandins play in the seminal fluid?
What role do prostaglandins play in the seminal fluid?
What is the primary composition of the seminal fluid from the seminal vesicles?
What is the primary composition of the seminal fluid from the seminal vesicles?
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During sexual arousal, what is the primary purpose of the secretion from the bulbourethral glands?
During sexual arousal, what is the primary purpose of the secretion from the bulbourethral glands?
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What happens to a zygote that inherits only a Y chromosome?
What happens to a zygote that inherits only a Y chromosome?
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What is the structure formed by the inactivation of one X chromosome in females?
What is the structure formed by the inactivation of one X chromosome in females?
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What is the role of TDF (testis-determining factor) in sexual differentiation?
What is the role of TDF (testis-determining factor) in sexual differentiation?
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Which duct develops into male accessory organs?
Which duct develops into male accessory organs?
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What occurs if the appropriate developmental signal for the medulla is absent?
What occurs if the appropriate developmental signal for the medulla is absent?
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Which of the following genes is activated by the SRY gene?
Which of the following genes is activated by the SRY gene?
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What does the presence of testosterone lead to during sexual differentiation?
What does the presence of testosterone lead to during sexual differentiation?
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In which scenario would both the Müllerian duct and Wolffian duct be patent?
In which scenario would both the Müllerian duct and Wolffian duct be patent?
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What hormonal change occurs if fertilization does not happen by day 22 of the menstrual cycle?
What hormonal change occurs if fertilization does not happen by day 22 of the menstrual cycle?
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What effect does progesterone have on the uterine lining during the menstrual cycle?
What effect does progesterone have on the uterine lining during the menstrual cycle?
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Which part of the ovarian cycle is characterized by the secretion of FSH from the anterior pituitary?
Which part of the ovarian cycle is characterized by the secretion of FSH from the anterior pituitary?
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Which pathway primarily involves the formation of progesterone in the corpus luteum?
Which pathway primarily involves the formation of progesterone in the corpus luteum?
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Which of the following occurs at the end of menstruation?
Which of the following occurs at the end of menstruation?
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What is the primary precursor for all ovarian steroids?
What is the primary precursor for all ovarian steroids?
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How does estrogen affect the fallopian tubes during the menstrual cycle?
How does estrogen affect the fallopian tubes during the menstrual cycle?
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What happens to the uterine lining when hormone levels fall due to the regression of the corpus luteum?
What happens to the uterine lining when hormone levels fall due to the regression of the corpus luteum?
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What changes occur in the uterus as a result of progesterone during pregnancy?
What changes occur in the uterus as a result of progesterone during pregnancy?
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What is the primary effect of increased osteoblast activity in the skeleton during puberty?
What is the primary effect of increased osteoblast activity in the skeleton during puberty?
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Which contraceptive method is considered the most effective for preventing pregnancy?
Which contraceptive method is considered the most effective for preventing pregnancy?
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What is a physiological change related to fat deposition during puberty?
What is a physiological change related to fat deposition during puberty?
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What is the role of the diaphragm in contraceptive methods?
What is the role of the diaphragm in contraceptive methods?
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What is one effect of progesterone on the breasts during the luteal phase?
What is one effect of progesterone on the breasts during the luteal phase?
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How does an increase in basal metabolic rate (BMR) during puberty affect the body?
How does an increase in basal metabolic rate (BMR) during puberty affect the body?
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Which of the following is a characteristic of sterilization as a contraceptive method?
Which of the following is a characteristic of sterilization as a contraceptive method?
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What is colostrum primarily composed of?
What is colostrum primarily composed of?
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What triggers the let-down reflex in lactation?
What triggers the let-down reflex in lactation?
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Which hormone's secretion declines after the placenta is expelled?
Which hormone's secretion declines after the placenta is expelled?
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How does suckling affect prolactin secretion?
How does suckling affect prolactin secretion?
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What role does progesterone play in breast development?
What role does progesterone play in breast development?
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What effect does taking estrogen have on prolactin secretion?
What effect does taking estrogen have on prolactin secretion?
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Which of the following hormones are essential together for full development of breasts?
Which of the following hormones are essential together for full development of breasts?
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What is the role of prolactin in both males and females?
What is the role of prolactin in both males and females?
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What physiological change occurs in minute ventilation during pregnancy due to progesterone?
What physiological change occurs in minute ventilation during pregnancy due to progesterone?
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How does the growing uterus affect respiratory function during pregnancy?
How does the growing uterus affect respiratory function during pregnancy?
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What effect does pregnancy have on renal blood flow and glomerular filtration rate?
What effect does pregnancy have on renal blood flow and glomerular filtration rate?
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Which hormones are primarily responsible for increased tubular reabsorption of salt and water during pregnancy?
Which hormones are primarily responsible for increased tubular reabsorption of salt and water during pregnancy?
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What happens to women's menstrual cycles during menopause?
What happens to women's menstrual cycles during menopause?
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What health risk increases due to the lack of estrogens during menopause?
What health risk increases due to the lack of estrogens during menopause?
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How does the body compensate for a decreased total excursion of the diaphragm during pregnancy?
How does the body compensate for a decreased total excursion of the diaphragm during pregnancy?
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Which factor is suggested to potentially contribute to renal vasodilation during pregnancy?
Which factor is suggested to potentially contribute to renal vasodilation during pregnancy?
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What is the primary role of human placental lactogen hormone (hPL) during pregnancy?
What is the primary role of human placental lactogen hormone (hPL) during pregnancy?
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What substances contribute to the formation of oestrogens in the placenta?
What substances contribute to the formation of oestrogens in the placenta?
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How does progesterone function in relation to the uterine endometrium during pregnancy?
How does progesterone function in relation to the uterine endometrium during pregnancy?
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What effect does human chorionic gonadotropin have on male foetal development?
What effect does human chorionic gonadotropin have on male foetal development?
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Which hormone is primarily involved in decreasing the contractility of the uterus to prevent early contractions?
Which hormone is primarily involved in decreasing the contractility of the uterus to prevent early contractions?
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What is the correct sequence of the sperm's route after formation?
What is the correct sequence of the sperm's route after formation?
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Which structure directly increases parasympathetic innervation to achieve an erection?
Which structure directly increases parasympathetic innervation to achieve an erection?
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What hormone does GnRH stimulate the anterior pituitary to release?
What hormone does GnRH stimulate the anterior pituitary to release?
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How does testosterone influence feedback mechanisms in the reproductive axis?
How does testosterone influence feedback mechanisms in the reproductive axis?
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What is the primary function of androgen-binding protein (ABP) synthesized by Sertoli cells?
What is the primary function of androgen-binding protein (ABP) synthesized by Sertoli cells?
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What is the role of inhibin produced during spermatogenesis?
What is the role of inhibin produced during spermatogenesis?
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Which enzyme precursor is important for the synthesis of sex steroids in Leydig cells?
Which enzyme precursor is important for the synthesis of sex steroids in Leydig cells?
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What primarily triggers the release of an ovum during the menstrual cycle?
What primarily triggers the release of an ovum during the menstrual cycle?
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During which phase of the menstrual cycle does the corpus luteum form?
During which phase of the menstrual cycle does the corpus luteum form?
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What happens to hormone levels if fertilization does not occur by day 22 of the menstrual cycle?
What happens to hormone levels if fertilization does not occur by day 22 of the menstrual cycle?
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What is the role of FSH at the end of menstruation?
What is the role of FSH at the end of menstruation?
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Which substance serves as the precursor for all ovarian steroids?
Which substance serves as the precursor for all ovarian steroids?
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What effect does estrogen have on the fallopian tubes?
What effect does estrogen have on the fallopian tubes?
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What is the primary function of trophoblast cells after fertilization?
What is the primary function of trophoblast cells after fertilization?
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What happens to the uterine lining when progesterone levels fall due to the regression of the corpus luteum?
What happens to the uterine lining when progesterone levels fall due to the regression of the corpus luteum?
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During which stage does the zygote transform into a morula?
During which stage does the zygote transform into a morula?
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Which pathway involves the formation of dehydroepiandrosterone (DHEA)?
Which pathway involves the formation of dehydroepiandrosterone (DHEA)?
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What structure does the inner cell mass of the blastocyst develop into?
What structure does the inner cell mass of the blastocyst develop into?
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What occurs during the menstruation phase of the menstrual cycle?
What occurs during the menstruation phase of the menstrual cycle?
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What is the role of uterine milk in early pregnancy?
What is the role of uterine milk in early pregnancy?
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What triggers the attachment of the blastocyst to the uterine wall?
What triggers the attachment of the blastocyst to the uterine wall?
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What does the morula consist of?
What does the morula consist of?
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How does the blastocyst interact with the endometrial cells?
How does the blastocyst interact with the endometrial cells?
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What event typically occurs 6 days post-fertilization?
What event typically occurs 6 days post-fertilization?
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Which extra-embryonic membrane degenerates early in human development?
Which extra-embryonic membrane degenerates early in human development?
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What is a significant characteristic of the blastocyst?
What is a significant characteristic of the blastocyst?
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What is the primary method through which the foetus excretes carbon dioxide?
What is the primary method through which the foetus excretes carbon dioxide?
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What is one of the known roles of human chorionic somatomammotropin (hCS) during pregnancy?
What is one of the known roles of human chorionic somatomammotropin (hCS) during pregnancy?
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During pregnancy, how does the level of glucose in the foetal blood compare to that in maternal blood?
During pregnancy, how does the level of glucose in the foetal blood compare to that in maternal blood?
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How do nutrients such as fatty acids primarily move from maternal blood to foetal blood?
How do nutrients such as fatty acids primarily move from maternal blood to foetal blood?
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What condition arises in about 4% of pregnant women due to elevated blood glucose levels?
What condition arises in about 4% of pregnant women due to elevated blood glucose levels?
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What is the function of trophoblast cells in the placenta concerning glucose transport?
What is the function of trophoblast cells in the placenta concerning glucose transport?
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Which of the following occurs if a pregnant woman has a genetic defect preventing hCS production?
Which of the following occurs if a pregnant woman has a genetic defect preventing hCS production?
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What substances, besides glucose, diffuse easily from maternal blood into foetal blood?
What substances, besides glucose, diffuse easily from maternal blood into foetal blood?
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What is a likely consequence of the foetus using as much glucose as the entire body of the mother?
What is a likely consequence of the foetus using as much glucose as the entire body of the mother?
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What happens to the transport of nutrients like glucose and fatty acids during the later stages of pregnancy?
What happens to the transport of nutrients like glucose and fatty acids during the later stages of pregnancy?
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Study Notes
Reproduction, Development, and Pregnancy
- Mammalian sex determination is regulated by chromosomes.
- Females have two X chromosomes (XX).
- Males have one X and one Y chromosome (XY).
- The testis-determining factor (TDF) is located on the Y chromosome.
- Embryonic testes secrete testosterone, which is responsible for the development of secondary sex organs and external genitalia.
- Absence of testes leads to female accessory sex organ development.
- An XXY zygote will become male.
- A zygote that inherits only a Y chromosome (YO) will die because the larger X chromosome contains essential genes that are missing from the Y chromosome.
- In a female fetus, one X chromosome in each cell is inactivated and condenses into a Barr body.
- Embryonic tissues are bipotential—meaning they cannot be identified morphologically as male or female.
- The bipotential gonad has an outer cortex and an inner medulla that has the potential to develop into a testis or an ovary.
- The medulla develops into a testis under the influence of the appropriate developmental signal.
- In the absence of the appropriate signal, the cortex differentiates into ovarian tissue.
Formation of Testes and Ovaries
- Male sex is determined by the presence of the Y gene (XY).
- In rare cases, XX male babies are found.
- One of the X chromosomes contains a segment of the Y chromosome.
- XY females were found to be missing the same portion of the Y chromosome as XX males.
- The gene for TDF is found on the short arm of chromosome Y.
- This gene is known as SRY (sex-determining region of the Y).
- An error in placing SRY in the X chromosome seems to occur in meiosis during sperm cell formation.
Development of Internal Organs
- The presence of a Y chromosome means the embryo will become male, even if the zygote also has multiple X chromosomes.
- An XXY zygote will become male. A zygote that inherits only a Y chromosome (YO) will die because the larger X chromosome contains essential genes that are missing from the Y chromosome.
- Once the ovaries develop in a female fetus, one X chromosome in each cell of her body is inactivated.
- The inactivated X chromosome condenses into a clump of nuclear chromatin known as a Barr body, which can be seen in stained cheek epithelium.
- The selection of the X chromosome to be inactivated during development is random.
- Before differentiation, the embryonic tissues are considered bipotential because they cannot be morphologically identified as male or female.
- The bipotential gonad has an outer cortex and an inner medulla. The medulla develops into a testis under the influence of the appropriate developmental signal. In the absence of that signal, the cortex will differentiate into ovarian tissue.
Production of Testes and Ovaries
- One part of the embryo's indifferent gonads can form testes.
- The other part can form ovaries.
- TDF directs the development of the indifferent gonads into testes.
- Absence of TDF causes the indifferent gonads to develop into ovaries.
- The embryonic gonads are initially bipotential—having the potential to develop into either testes or ovaries.
- The presence of the Y chromosome determines the development of testes.
- In the absence of the Y chromosome, the gonads develop into ovaries.
- The Wolffian duct develops into male accessory organs:
- epididymis
- ductus deferens
- seminal vesicles
- ejaculatory duct
- The Müllerian duct develops into female accessory organs:
- uterus
- uterine tubes
- The indifferent gonads begin to develop into testes or ovaries through the secretion of testosterone and MIF.
Male Reproduction
- The testes are oval-shaped primary male reproductive organs that are suspended inside a sac (scrotum) by the spermatic cord.
- The spermatic cord is composed of the vas deferens, arteries, veins, lymphatics, and nerves.
- Testes produce sperm (exocrine function) and testosterone (endocrine function).
- Sperm is produced in seminiferous tubules.
- Interstitial cells produce testosterone.
- The testes descend into the scrotum just before birth through the inguinal canal.
- The interior of the testis is divided into 250 lobules.
- Each lobule contains 1 to 4 highly coiled, convoluted tubules called seminiferous tubules.
- Interstitial cells are found in the connective tissue surrounding the seminiferous tubules.
- The tubules (seminiferous) unite to form a complex network of channels called the rete testis.
- The rete testis gives rise to several ducts that join the epididymis.
Male Reproductive System
- The main structures are
- Testes
- Reproductive ducts
- epididymis
- vas deferens
- ejaculatory duct
- urethra
- Accessory glands
- seminal vesicles
- prostate gland
- bulbourethral glands
- Supporting structures
- scrotum
- penis
- spermatic cords
Spermatogenesis
- Spermatogenesis involves 5 stages:
- Spermatogonia-mitosis
- primary spermatocyte- meiosis I
- secondary spermatocyte- meiosis II
- spermatid- maturation of sperm
- spermatozoa
- Sertoli cells secrete factors that regulate spermatogenesis and spermiogenesis.
- Spermatids remain embedded in the apical membrane of Sertoli cells while they complete transformation into spermatozoa.
Functions of Sertoli Cells
- Support: Provide nutrients and remove waste materials from spermiogenesis.
- Phagocytotic: Remove residual bodies and cellular material shed by spermatids.
- Secretory: Secrete Mullerian-inhibiting substance & Androgen binding protein.
- Protective: Form the blood-testis barrier.
Composition of Semen
- Component-
- sperm
- mucus
- water
- buffers
- nutrients
- Function-
- gamete
- lubricant
- neutralizes acidic environment of vagina
- nourish sperm
- Source-
- seminiferous tubules
- bulbourethral glands
- accessory glands
Male Reproduction - DHT
- DHT is needed for the development of the penis, spongy urethra, and prostate.
- Testosterone directly stimulates the Wolffian duct derivatives, such as the epididymis, ductus deferens, seminal vesicles, and ejaculatory duct.
Female Reproduction
- Ovaries are paired abdominal organs, one for each reproductive cycle.
- They produce one ovum per cycle, which the ovarian wall expels.
- The ovum enters the abdominal cavity.
Fallopian Tubes (Oviducts)
- These tubes are 10-15 cm long
- At ovulation, the ovum enters the tube through the fimbriated end.
- The ovum travels along the tube to the uterus, facilitated by cilia and smooth muscle.
- If sperm is present, fertilization may occur within the Fallopian tube.
- Secretions from the tube wall nourish the zygote on its way to the uterus.
- Estrogen and progesterone influence movement of cilia and smooth muscle contraction; secretion of mucus from mucosal glands.
- Estrogen & progesterone influence.
Uterus (Womb)
- The pear-shaped muscular organ is continuous with the uterine tube.
- It is located between the bladder and the rectum.
- It has three layers:
- Perimetrium (outer connective tissue)
- Myometrium (smooth muscle)
- Endometrium (inner epithelial)
Cervix (Neck)
- The cervix connects the uterine cavity with the vagina.
Vagina
- The vagina connects the cervix with the external environment.
- The vagina, uterus, and uterine tubes form accessory female sex organs, affected by gonadal steroid hormones.
Ovarian Cycle/Hormonal Control of Ovaries
- During puberty, the hypothalamus secrets GnRH (gonadotrophin-releasing hormone) to stimulate the anterior pituitary.
- The anterior pituitary secretes FSH and LH to stimulate follicle development in the ovary and for ovulation.
- FSH stimulates follicle development in the ovary.
- LH is for ovulation.
Oogenesis
- The formation and growth of an ovum within the ovary.
- Germ cells migrate into the ovaries during embryonic development.
- By the end of gestation, cells divide through meiosis and form primary oocytes (2n).
- At birth, about two million primary oocytes are contained in a hollow ball of cells—an ovarian (primordial) follicle.
- About 400,000 primary oocytes remain at puberty, and about 400 of them will mature during a woman's reproductive lifespan.
Ovarian Cycle
- The ovaries consist of an outer cortex and an inner medulla.
- The cortex has developing ovarian follicles throughout the cortex.
- The medulla consists of blood and lymphatic vessels along with nerve fibers.
Menstrual Cycle Overview
- The cycle is divided into phases based on changes in the ovaries and endometrium.
- Ovaries: Follicular phase (menstruation day 1 until ovulation), Luteal phase (ovulation until day 1 of menstruation)
- Endometrium: Menstrual, Proliferative, & Secretive phases
Hormonal Control of the Menstrual Cycle
- The levels of FSH, LH, estrogen, and progesterone fluctuate during the menstrual cycle. These hormones are produced by the anterior pituitary of the mother's body and the ovary to control the process of menstruation.
Ovulation
- FSH stimulates graafian follicle to enlarge.
- A thin-walled blister forms on the surface of the ovary.
- Oestrogen secretion increases with growth.
- Rapid estrogen increase triggers LH secretion on day 13.
- LH surge triggers follicle rupture on day 14.
- Ovulation occurs, and the secondary oocyte is released.
Luteal Phase
- Following ovulation, the empty follicle is stimulated by LH.
- It forms the corpus luteum, which secretes progesterone and oestrogen.
- Progesterone levels rise rapidly following ovulation, peaking in the luteal phase.
- The peak is approximately one week after ovulation.
Corpus Luteum
- Progesterone and estrogen levels increase.
- Negative feedback on LH and FSH secretion.
- Suppresses FSH secretion and actions.
- Retards new follicle growth, avoiding multiple ovulations.
If No Fertilization
- If no fertilization occurs (day 22), the corpus luteum regresses.
- Inhibin secretion decreases.
- Progesterone and oestrogen levels fall.
- New follicles begin to grow.
- The withdrawal of ovarian hormones causes menstruation, and a new cycle begins.
Male Fertility
- Sex steroids are produced in the male reproductive tract
- Testosterone is the primary androgen.
- Androgen synthesis depends on cholesterol.
- It is converted to different steroid hormones through specific enzymatic steps.
- The process is called steroidogenesis.
- During spermatogenesis, the testes produce several proteins including androgens which encourage development of secondary sexual characteristics.
- These are stimulated by the hormones FSH and LH.
Summary of Menstrual Cycle
- Egg release and endometrial changes: Lining is discharged, follicle matures, ovulation, uterine lining continues to thicken to prepare for embryo implantation, if no fertilization, the unfertilized egg dies.
- Day 1-5: Menstruation-- Lining is discharged.
- Day 6-14: Proliferative Phase -- Follicle matures, uterine lining begins to thicken.
- Day 14-28: Secretory Phase -- Ovulation occurs and uterine lining continues to thicken to nourish a possible embryo implantation, if fertilization doesn't occur, the corpus luteum deteriorates causing the uterine lining to shed.
Stages of Pregnancy
- First trimester (0-12 weeks): Three embryonic tissue layers form, cellular differentiation begins to form organs, embryo is about 5mm long, paired somite segments, major organ systems form, limbs buds develop, embryo becomes a fetus by the seventh week.
- Second trimester (13-28 weeks): Fetus increases in size, bony parts of the skeleton begin to form, fetal movements can be felt by the mother, sex differentiation begins.
- Third trimester (29-40 weeks): Fetus increases in size; circulatory and respiratory systems mature in preparation for air breathing; fetal growth uses a large amount of maternal protein and calcium intake; maternal antibodies pass to the fetus during the last month, conferring temporary immunity.
Labour and Birth
- Labour = powerful contractions of the uterus are needed to expel the fetus.
- Two agents stimulate these contractions: oxytocin and prostaglandins.
- Oxytocin is produced in hypothalamus, released into posterior pituitary, and also produces contractions via the uterus.
- Prostaglandins (PG2 and PG2) COX-2—these begin contractions.
- Labour can be induced artificially by injecting oxytocin or inserting prostaglandin into the vagina.
- Activation of foetal adrenal cortex initiates labour.
- Estrogen is important in the initiation of labour by priming the uterine sensitivity to oxytocin.
- The human placenta cannot synthesize estrogen.
- Prostaglandins are a primary cause of menstrual cramps and have been used in early pregnancy to induce abortion.
- Prostaglandins reinforce uterine contractions induced by oxytocin during labour and delivery.
Chorionic Membranes
- Between day 7 and 12, the blastocyst becomes completely embedded in the endometrium.
- The chorion is two cells thick (inner cytotrophoblast, outer syncytiotrophoblast).
- The inner cell mass forms two layers (ectoderm and endoderm).
- The embryo is two cells thick, separated from the cytotrophoblast by the amniotic cavity.
Placenta and Amniotic Sac
- During implantation, the endometrium undergoes changes, including growth of cells and glycogen accumulation.
- This cellular growth and glycogen accumulation is known as the decidual reaction.
Enzymes and Membrane
- Enzymes from the villi break down the walls of maternal blood vessels until the villi are surrounded by pools of maternal blood.
- The blood of the embryo and the mother do not mix, but substances such as nutrients, gases, and wastes cross the placental membranes by diffusion.
- The placenta continues to grow during pregnancy (about 20cm diameter).
- The placenta receives 10% of the total maternal cardiac output.
hCG
- hCG is produced by the developing placenta
- It prevents the corpus luteum from degrading and allows for continued progesterone and estrogen production.
- hCG rises in early pregnancy
- hCG levels in urine are used for home pregnancy tests.
hCS
- Secreted by the placenta
- Structurally related to growth hormone and prolactin
- Important for milk production.
- Influences maternal glucose and fatty acid metabolism to support fetal growth
Other Metabolic Substrates
- Other metabolic substrates needed by the fetus diffuse into the fetal blood in the same manner as oxygen and glucose.
- In later pregnancy, the fetus uses as much glucose as the entire body of the mother.
Waste Product Excretion
- Waste products are excreted from the fetus into the maternal blood through diffusion.
- These products include nonprotein nitrogens (urea, uric acid, and creatinine), but creatinine has a higher concentration in the fetal blood.
Amniotic Fluid
- The volume of amniotic fluid is between 500 milliliters and 1 liter.
- Isotope studies show amniotic fluid's water is replaced every 3 hours, and electrolytes are replaced every 15 hours.
- A large portion of the fluid comes from foetal renal excretion.
The Three Trimesters
- First trimester (0-12 weeks): Cellular differentiation, main organ systems form, embryo becomes a fetus.
- Second trimester (13-28 weeks): Fetus grows in size, bony parts of the skeleton form, fetal movement is noticeable.
- Third trimester (29-40 weeks): Fetus continues to grow in size, circulatory and respiratory systems mature, maternal antibodies are transferred to the fetus.
Labour and Birth
- Labour involves powerful uterine contractions to expel the fetus.
- Oxytocin and prostaglandins are important agents in stimulating these contractions.
- Oxytocin is produced in the hypothalamus and released into the pituitary gland and produced by the uterus.
- Prostaglandins cause uterine contractions and are also a cause of menstrual cramps.
- Uterine contractions from prostaglandins and oxytocin, along with the increased sensitivity to these agents, initiate labour.
- The activation of the foetal adrenal cortex initiates labour.
- Oestrogen plays an important role in labour initiation by priming the uterus to be sensitive to oxytocin.
Lactation
- Milk production is stimulated by prolactin from the anterior pituitary gland.
- Prolactin secretion is mainly controlled by prolactin-inhibiting hormone (PIH), which is believed to be dopamine, secreted by the hypothalamus.
- During pregnancy, oestrogen and progesterone levels are high; however, they inhibit lactation.
- When the placenta is expelled, oestrogen levels decline, and prolactin secretion increases.
- Suckling activates sensory endings in the breast that stimulate the release of oxytocin—the milk-ejection reflex.
- Prolactin and oxytocin, along with other hormones, influence mammary gland development and milk production.
Increased Corticosteroid Secretion
- Glucocorticoid levels increase in pregnancy.
- These hormones help mobilize amino acids in the mother for use by the fetus in tissue synthesis.
- The production of aldosterone, increasing the retention of sodium in the blood by the kidneys, also increases.
- Thyroid gland secretion increases, as does parathyroid gland secretion, which causes increased calcium absorption from the mother's bones.
Response of the Mother's Body to Pregnancy
- Weight gain during pregnancy: The average weight gain is due to increases in foetus, amniotic fluid and membranes, the uterus and the breasts, and extra-cellular/blood fluid.
- Metabolism: The basal metabolic rate of the pregnant woman increases by about 15%.
- Changes in nutrition during pregnancy and the mother's circulatory, respiratory, kidney, and pelvic changes. All these changes are essential to prepare for the coming delivery.
Nutrition during Pregnancy
- During the last two months of pregnancy, the dramatic growth of the fetus causes the mother's body to require an increased intake of proteins, calcium, phosphates, and iron.
- The mother's body has anticipated these needs by storing these substances in the placenta and other storage depots of her body.
- Maternal blood volume and cardiac output increase substantially during pregnancy, mainly during the last half of pregnancy.
- These changes help offset the increase in the uterus causing the total excursion of the diaphragm to decrease, thus increasing the mother's respiratory rate.
Maternal Respiration During Pregnancy
- Increased basal metabolic rate in pregnancy results in a greater consumption of oxygen and consequently an increased production of carbon dioxide in the mother.
- High levels of progesterone increase the respiratory center's sensitivity to carbon dioxide.
- As a response, a 50% increase in minute ventilation occurs in pregnant women with a concurrent decrease in arterial PCO2.
- The growing uterus presses against abdominal contents, reducing the diaphragm's excursion, causing an increase in respiratory rate to meet the increased ventilation needs.
Maternal Kidney Function During Pregnancy
- The rate of urine formation slightly increases.
- The renal tubules' reabsorptive ability for certain electrolytes (Na+, Cl-, and water) increases.
- Renal blood flow and glomerular filtration rates rise.
- Increases are due to the increased production of salt and water-retaining hormones, notably steroid hormones like estrogen and aldosterone, produced by the placenta and adrenal cortex. This helps in compensating the increased tubular reabsorption of water and salt, and maintaining fluid balance for both mother and fetus.
Menopause
- Ages 40-50 years.
- Cycles become irregular/cease.
- Hot flushes, irritability, fatigue, anxiety, emotionality.
- Oestrogen output decreases due to follicle depletion.
- Lack of oestrogen increases risk of osteoporosis and causes bone loss and/ or fractures.
- Absence of ovarian steroids causes symptoms.
- Circulating LH/FSH increase, but they are continuous, rather than cyclical.
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Description
Test your knowledge on the functions and roles of various components in the human reproductive system. This quiz covers seminal fluid, sexual differentiation, and the anatomy involved in male development. Examine concepts such as fructose in seminal fluid and the implications of genetic factors in sexual differentiation.
