Bio 30 - 6b_Reproduction Development Student PDF
Document Details
Uploaded by HearteningDulcimer
Tags
Summary
This document covers human reproduction and development, focusing on the structures and functions of the AMAB reproductive system, including testes, seminiferous tubules, and glands, as well as comparing sperm and eggs. The document also discusses fertilization and includes questions on related topics. This is not a past paper or practice questions.
Full Transcript
Bil 30-B Hum roto & Devme 2 Hum ul Rodon A. Production of Gametes 1. Gametes --> sex cells containing 23 chromosomes instead of 46 found in all human cells 2. Eggs and sperm are said to be haploid containing only one copy of each chromosome...
Bil 30-B Hum roto & Devme 2 Hum ul Rodon A. Production of Gametes 1. Gametes --> sex cells containing 23 chromosomes instead of 46 found in all human cells 2. Eggs and sperm are said to be haploid containing only one copy of each chromosome 3 Hum ul Rodon A. Fertilization - → Unification of egg and sperm to produce a zygote or fertilized egg (diploid). - 23 in sperm + 23 in egg - → 46 in fertilized egg. 4 A Bri al ‘Gne Spr’ Assigned Male at birth - AMAB Assigned Female at Birth - AFAB 5 1. Pep it Pis Am - AM Human Reproduction & Development #1 Tod’ Obet - Identify the structures in the human AMAB reproductive system and describe their functions; i.e., testes, seminiferous tubules, interstitial cells, Sertoli cells, epididymides, vasa (ductus) deferentia, Cowper’s glands, seminal vesicles, prostate gland, ejaculatory duct, urethra, penis. - Distinguish sperm and egg from their supporting structures; i.e., seminiferous tubules, interstitial cells, Sertoli cells, follicle, corpus luteum. 7 Repci Sym Oer Humans reproduce by sexual reproduction. The specialized reproductive cells of humans are produced by, unite in, and develop within the organs of the AMAB and AFAB reproductive systems. The AMAB gonads, the testes, produce AMAB sex cells called sperm. The AFAB gonad, the ovary, produces eggs. The fusion of a AMAB and AFAB sex cell occurs within the AFAB reproductive system, in a process called fertilization, which produces a single-celled zygote. The zygote divides many times to form an embryo, which in turn continues to grow into a fetus. 8 The ep’ Repci Sym AMAB and AFAB sex organs both originate in the abdominal cavity and are almost indistinguishable until about the third month of embryonic development. At that time, the genes of the sex chromosomes cause differentiation. During the last two months of fetal development, the testes descend through a canal into the scrotum. A thin membrane forms over the canal, thereby preventing the testes from re-entering the abdominal cavity. 9 The ep Cot. Occasionally, an injury may cause the rupture of this membrane that forms between the scrotum and the abdomen, producing an inguinal hernia. The hernia can be dangerous because a segment of the small intestine can be forced into the scrotum. The small intestine creates pressure on the testes, and blood flow to either the testes or small intestine may become restricted. 10 11 Pen ol’ Rrote Srre Testes: the AMAB gonads, or primary reproductive organs; AMAB sex hormones and sperm (the AMAB sex cells or gametes) are produced in the testes. Scrotum: the sac that contains the testes. The temperature in the scrotum is a few degrees cooler than body temp. – this important temp. difference allows for the development of sperm. – If the testes fail to descend into the scrotum, the AMAB will be sterile. Vas deferens: tube that conducts sperm toward the urethra. Ejaculatory duct: a tubule formed at the union of the vasa deferentia and the seminal vesicle ducts and opening into the urethra. Glans penis: sensitive bulbous structure at the distal end of the penis. 12 13 Q- If o ne t ve filin et t ud to cord i AM rediv su? Q- ha co f nes se cr bo f to se (dion/cotto)? Q- esb e re d rur pe cs l as m tes to xen vim. Questions? 14 Repci Sttu c. During sexual excitement, stimulation of the parasympathetic nerve causes the arteries leading to the penis to dilate, thereby increasing blood flow. Spongy tissue surrounding these arteries also fills with blood. The veins that carry blood away from the penis compress, thus slowing blood flow out of the penis. Any damage to the parasympathetic nerve can cause impotency, in which the penis fails to become erect. – Other causes, such as hormone imbalance and stress, have also been associated with impotence. 15 Repci Sttu c. Sperm is produced in the testis. They travel through the vas deferens (plural vasa deferentia) until they reach the ejaculatory duct. Any blockage of the vas deferens will Vasectomy: prevent the movement of sperm from a surgical form of birth control in which the vas the testes to the external environment. deferens from each testicle is cut and tied. 16 Repci Sttu c. The ejaculatory duct propels the movement of sperm and fluids, called semen, into the urethra, which also serves as a channel for urine. Semen (seminal fluid): a secretion of the AMAB reproductive organs that is composed of sperm and fluids (contributed from by secretions of three glands). A sphincter regulates the voiding of urine from the bladder. At any given time, the urethra conducts either urine or semen, but never both. 17 18 “ Coming soon - a discussion of testicular & prostate cancer Testicular Cancer |LINK | Prostate Cancer |LINK | 19 Spetes The inside of each Seminiferous tubules: testis is filled with coiled ducts found within the seminiferous tubules testes, where immature sperm that measure cells divide and differentiate. approximately 250 m in length! Seminiferous tubules are the site of spermatogenesis, which is the formation of sperm cells. 20 Spetes on. It takes 9 to 10 weeks for the spermatocytes to differentiate into sperm cells. - The seminiferous tubules are lined with sperm-producing cells called spermatogonia. During spermatogenesis, spermatogonia (46 chromosomes) divide to form to spermatocytes (46 chromosomes) → = mitosis - Spermatocytes then differentiate into spermatids (23 chromosomes), which are immature sperm cells → = meiosis 21 Spetes on. Specialized cells in the seminiferous tubules, called Sertoli cells, nourish the developing sperm cells until they are mature. - Sertoli cell: a cell that provides metabolic and mechanical support to developing sperm cells. Sertoli cells also provide a barrier between the blood and the seminiferous tubules. This barrier controls the entry and exit of hormones, nutrients, and other chemicals into the seminiferous tubules, which protects the developing sperm cells. If the barrier is damaged and sperm enter the bloodstream, the body can develop antibodies against its own sperm. This can result in a decreased ability to fertilize egg cells. 22 23 Spetes on. Although sperm cells are produced in the testes, they mature in the epididymis, a compact, coiled tube attached to the outer edge of the testis. - Epididymis: structure located along the posterior border of the testis, consisting of coiled tubules that store sperm cells. Sperm cells in the epididymis begin swimming motions within four days. It is believed that some defective sperm cells are destroyed by the immune system during their time in the epididymis. 24 Spe l Built for motion, the sperm cell is streamlined with only a small amount of cytoplasm surrounding the nucleus. - Limited cytoplasm also means a limited energy reserve. - Mitochondria are found between the nucleus and the flagellum, the organelle that propels the sperm cell. - The acrosome caps the head of the sperm cell. It contains enzymes that dissolve the gelatinous outer coating surrounding the egg and allows the sperm to penetrate the egg. 25 Sem Flu Sperm leave the body as part of a fluid, semen, which provides a swimming medium for the flagellated sperm. - Ejaculation is the process by which the semen leaves the body via the penis. - The vasa deferentia, seminal vesicles, ejaculatory duct, and prostate gland contract, forcing the semen to the base of the penis. - Strong muscular contractions force the semen into the urethra and out of the penis. - Every time a man ejaculates, between 3 and 4 mL of fluid, containing approximately 500 million sperm cells, are released. 26 Sem Flu t. The seminal fluids are secreted by three glands along the vasa deferentia and ejaculatory duct. - Fructose acts as an energy source for sperm cells. 1. Seminal Vesicles secrete fluid that contains - Prostaglandins act as a chemical signal in the AFAB system, triggering the rhythmic contraction of fructose and prostaglandins. smooth muscle along the reproductive tract. - It is believed that the contraction of muscles along **‘s’ is for ‘sugar’** the AFAB reproductive pathways assists the movement of sperm cells toward the egg. 27 Sem Flu t. The seminal fluids are secreted by three glands along the vasa deferentia and ejaculatory duct. 2. Prostate Gland secretes an alkaline buffer that protects sperm cells against the acidic environment of the vagina. **‘p’ is for ‘protection’** 28 Sem Flu t. The seminal fluids are secreted by three glands along the vasa deferentia and ejaculatory duct. 3. Cowper’s (bulbourethral) glands secrete mucus-rich fluids prior to ejaculation. The fluids are thought to protect the sperm cells from the acids found in the urethra associated with the passage of urine. The fluid may also assist sperm movement **‘c’ is for ‘cleans’** 29 - Although sperm cells can exist for many weeks in the epididymis, life span is reduced when they come in contact Spe c with the various fluids in the semen. - At body temperature, sperm cells will live only 24 to 72 hours. Did you know semen is: - When stored at –100 °C, sperm cells have been known to remain viable for 60% secretions from the seminal vesicle many years. 30% secretions from the prostate 10% secretions from the Cowper’s gland 30 Q# 1-2 on . 514. Q# 3-4 on . 515. Q# 5 on . 516. Q - ic 1 tal cad is a dre pol h ol cu d it d aff fel. Practice 32 2. Testo Bse ma Regin - AM Human Reproduction & Development #2 Tod’ Obet - Describe the chromosomal factors and hormonal influence on the formation of the gonads and reproductive organs in the AFAB and AMAB embryo and fetus; i.e., Y chromosome and role of testosterone. 34 AM orl Cor te R.. The structures and functions that we have talked about thus far are referred to as primary sexual characteristics. Primary sexual characteristics are physical characteristics directly involved in reproduction and are present at birth. The maturation and functioning of the AMAB reproductive system is regulated by a number of hormones. 35 AM ecr Sel Caciss AFAB AFAB As an AMAB reaches puberty, the levels of these hormones change, which initiates the development of secondary sexual characteristics. Secondary sexual characteristics are external features, other than the reproductive organs, that differ between mature AMAB and AFAB. 36 AM esto Testosterone is the primary AMAB sex hormone. It is produced in the interstitial cells (Leydig) – which are found between the seminiferous tubules within the testes Testosterone chemical formula = C 19 H 28 0 2 37 AM esto Stimulates the maturation of the testes and penis. Stimulates spermatogenesis. Promotes the development of secondary sex characteristics: – such as facial and body hair; the growth of the larynx (which causes the lowering of the voice); and the strengthening of muscles. Increases the secretion of body oils. – This has been linked to the development of acne in AMABs as they reach puberty. Once AMABs adjust to higher levels of testosterone, skin problems decline. – Increased oil production can also create body odour. Increased libido (sex drive) and aggressive behaviour. 38 AM orl Cor y Gad The hypothalamus and pituitary gland in the brain control the production of sperm and AMAB sex hormones (ie: testosterone) in the testes. Gonadotropin-releasing hormone (GnRH) is produced by the hypothalamus. – stimulates the anterior pituitary gland to secrete and release follicle-stimulating hormone (FSH) and luteinizing hormone (LH) 39 40 AM ffec f Hon Tars The anterior pituitary gland produces and stores the gonadotropic hormones (gonadotropins) that regulate the functions of the testes. There are two gonadotropins: - follicle-stimulating hormone (FSH) - luteinizing hormone (LH) In AMAB: FSH stimulates the production of sperm cells in the seminiferous tubules LH promotes the production of testosterone by the interstitial cells 41 AM Horl Cor Riw 42 AM orl Fec Interconnecting negative feedback systems ensure that adequate numbers of sperm cells and constant levels of testosterone are maintained. Beginning at puberty, the hypothalamus secretes GnRH when testosterone levels are low. GnRH activates the anterior pituitary gland to secrete FSH and LH. FSH acts directly on the sperm-producing cells of the seminiferous tubules. Sertoli Cells release inhibin as a result (peptide hormone) LH stimulates testosterone production. Testosterone also stimulates spermatogenesis. 43 Testosterone is used in the production of anabolic steroids. Q - Discuss how the presence of excessive amounts of testosterone could affect a human, both in terms of expected side effects and changes to the hormonal feedback system. 44 AMA B AMAB 45 AM nay Conl Gi Nte Practice 46 3. Pep it Vin Aom - AF Human Reproduction & Development #3 Tod’ Obet - Identify the structures in the human AFAB reproductive system and describe their functions; i.e., ovaries, Fallopian tubes, uterus, endometrium, cervix, vagina. - Distinguish … egg(s) from their supporting structures; i.e. … follicle, corpus luteum. 48 Vag Pel’ Rerti Ss Just like AMAB, secondary sexual characteristics begin to develop in AFAB during puberty as a result of hormonal stimulation. - the development of breasts - widening of the hips - growth of hair in the armpits and pubis AMAB AMAB AMAB 49 Vag Pel’ Rerti Ss During fetal development paired ovaries form in the same abdominal region as the testes - Like the similarly shaped testes, the ovaries descend, but unlike the testes, which come to lie outside of the abdominal cavity, the ovaries remain in the pelvic region. - At birth, oocytes (immature ova) are already present within the ovary. - During their reproductive years, AFAB follow a complicated sexual cycle, in which one ovum matures approximately every month. 50 Vag Pel’ Aat Ovary: - gonad or reproductive organ - homologous to the testes - AFAB sex hormones and egg cells (ova) are produced in the ovary. Fallopian tubes (oviducts): - Paired tubes that provide a passageway to the uterus. Endometrium - At the ovarian ends of each Fallopian tube are finger-like projections called fimbriae, whose motion creates a current that sweeps a released ovum into the fallopian tube. 51 Vag Pel’ Aat c. Uterus (womb): - The hollow, muscular, inverted pear-shaped organ located between the bladder and the anus. - The embryo and fetus develop in the uterus during normal pregnancies. - The uterus is composed of two major tissues Endometrium - a muscular outer lining - a glandular inner lining of the uterus, known as the endometrium. 52 Vag Pel’ Aat c. Cervix: - a muscular band that separates the vagina from the uterus. Vagina: - A muscular, hollow canal that connects the uterus to the outer environment; sexual intercourse occurs Endometrium here; also serves as the birth canal. - The vagina is acidic, creating a hostile environment for microbes that might enter the reproductive system. 53 54 Vag Pel’ Etel Aom Vulva: the external genitalia, includes the following tissues, Mons pubis: - rounded mass of fatty tissue lying over pubic joint - usually more pronounced than AMAB Labia majora: - enclose and protect the other external reproductive organs - contain sweat and oil-secreting glands , after puberty, become covered with hair. Labia minora: - lie just inside the labia majora and surround the openings to the vagina and urethra. Clitoris: - the two labia minora meet at the clitoris - a small protrusion, sensitive to stimulation and can become erect - covered by a fold of skin called the prepuce Bartholin's glands: - located beside the vaginal opening and produce a fluid (mucus) secretion. 55 Note the location of the external anatomy in this diagram. 56 57 58 Tub at - Similar to a vasectomy, tubal ligation is a surgical method of sterilization. - During tubal ligation, the surgeon cuts and then ties off the Fallopian tubes. Q - How would this prevent fertilization? - Approximately 60% of the women who have had the procedure reversed become pregnant. 59 “ Women should have Pap Tests regularly starting at age 21, or 3 years after becoming sexually active, whichever is later. - Alberta Health Services 60 Cerl Car H Cervical cancer is a major form of cancer affecting people with a uterus. HPV (Human Papillomavirus) is a leading contributor to cervical cancer. (100 types - 14 lead to cancer) - Types 16 & 18 cause ~70% of cervical cancers and pre-cancerous lesions - These types are protected against in the HPV vaccine Early detection by a Pap test greatly improves the chances of curing this form of cancer. - Like skin cells and the cells that line your mouth, cervical cells slough off. To collect a sample for a Pap test, a physician simply uses a swab to collect cells from the cervix. These cells are then checked for abnormalities that could indicate cancer. Oogis & Outo The ovum is much larger than sperm cells. An ovum is packed with nutrients, so that when it is fertilized it can divide rapidly. Q- What is the reason the ovum has so many more nutrients? While millions of sperm cells are manufactured every day, usually only one ovum is produced in Q- What is the overall process called that reduces chromosome at a time count from 46 → 23? - approx. once every 28 days. 62 Oogis Oogenesis is the formation and development of a mature ovum. In humans, oogenesis occurs in specialized structures in the ovaries, called follicles. A follicle contains two types of cells: - one primary oocyte - the cells of the granulosa - the layer of cells that forms the wall of a follicle. - provide nutrients for the developing oocytes. 63 An oocyte just before ovulation … 64 Oogenesis begins when granulosa cells surrounding the primary oocyte begin to divide. As the primary oocyte (46 chromosomes) undergoes meiosis I, the cytoplasm and nutrients are unequally divided between daughter cells. - The daughter cell that receives most of these things is called the secondary oocyte (23 chromosomes). The other cell is referred to as the first polar body and it dies. Granulosa cells continue to divide and a fluid-filled cavity forms around the secondary oocyte. Once the follicle reaches maturity, it ruptures (due to enzyme activity) and the secondary ootid is released from the ovary. This process is referred to as ovulation. Surrounding follicle cells remain within the ovary and are transformed into the corpus luteum, which secretes If pregnancy does not occur, the hormones (estrogen and progesterone) essential for corpus luteum degenerates after pregnancy. about 10 days. 65 Upon its release from the ovary, the secondary oocyte is swept into the funnel-shaped end of the Fallopian tube by the fimbria. The secondary oocyte is moved along the Fallopian tube by cilia where, if healthy sperm are present, it will become fertilized. The secondary oocyte will then undergo another unequal division of cytoplasm and nutrients (meiosis II) and develop into the fertilized ovum only after fertilization. The cell that retains most of the cytoplasm and nutrients becomes the ovum, and the other cell becomes the second polar body, which also dies. If the secondary oocyte is not fertilized, it will deteriorate within 24 hours and die. When this occurs, the AFAB will undergo a menstrual cycle. 66 67 AFAB 68 AF nay Suc & Funn - Col, Lal, A fut Stan Q# 1-2 p 522 Practice 69 4. Esog & Pogro Bed Horl Reti - AF Human Reproduction & Development #4 Tod’ Obet - Describe the role of hormones, i.e., gonadotropic-releasing hormone (GnRH), follicle stimulating hormone (FSH), luteinizing hormone (LH), estrogen, progesterone, testosterone, in the regulation of primary and secondary sex characteristics in AFAB and AMAB. - Identify the principal reproductive hormones in the AFAB and explain their interactions in the maintenance of the menstrual cycle; i.e., estrogen, progesterone, FSH, LH. 71 Horl Re. & Te nra Cce Along with the development of secondary sexual characteristics, puberty also initiates the menstrual cycle, which includes oogenesis, ovulation, and thickening and shedding of the endometrium. The menstrual cycle lasts an average of 28 days (although variation in this cycle is common) and is repeated throughout a woman’s reproductive lifetime. - The cycle is regulated by changes in the levels of various hormones & can be divided into four distinct phases: - flow phase - follicular phase - ovulatory phase - luteal phase 72 73 The ta Cye c. 1. Flow phase - AKA menstruation - (~days 1 – 5): Shedding of the endometrium during the menstrual cycle. Drop in hormone levels initiates uterine contractions which separate the endometrial layer. 74 The ta Cye c. 2. Follicular phase - (~days 6 – 13): The development of follicles within the ovary before ovulation. As follicles develop, the hormone estrogen is secreted, increasing the estrogen concentration in the blood. - Estrogen: - hormone that activates development of AFAB secondary sex characteristics, and increased thickening of the endometrium during the menstrual cycle. 75 The ta Cye c. 3. Ovulatory phase - (~day 14) the secondary oocyte bursts from the ovary (= ovulation). A positive feedback loop for estrogen spikes just prior to ovulation with FSH and LH spiking during ovulation 76 The ta Cye c. 4. Luteal phase - (~days 15 – 28) Characterized by the formation of the corpus luteum (from follicular cells remaining in the ovary) following ovulation. It prepares the uterus to receive a fertilized egg. 77 The ta Cye c. 4. Luteal phase Estrogen levels begin to decline when the oocyte leaves the ovary, but are somewhat restored when the corpus luteum forms. - The corpus luteum secretes both estrogen and progesterone. - Progesterone: hormone produced primarily by the corpus luteum, that induces changes in the endometrium during the menstrual cycle. Progesterone continues to stimulate the endometrium and prepares the uterus for the implantation and development of an embryo. It also inhibits further ovulation, prevents uterine contractions, and firms the cervix to prevent expulsion of the fetus. 78 The ta Cye c. 4. Luteal phase Should fertilization of an ovum not occur, levels of estrogen and progesterone will decrease, thereby causing uterine contractions. These uterine contractions make the endometrium pull away from the uterine wall. The shedding of the endometrium marks the beginning of the next flow phase, and the AFAB menstrual cycle starts all over again. 79 Diffres we Rrut Sses Penis People AMAB Vagina People AFAB Gametes - Testes continually replenish sex cells - Ovaries undergo continual decline after - Most sperm cells developed go on to the onset of puberty become mature functioning sperm cells - Many developed follicles -> only a single follicle becomes dominant and reachers maturity Age - Reaching sexually marturity after - Reaching sexually marturity after pubescence pubescence - Quantity and motility of sperm - Between the ages of about 12 and 50 in decrease continually (~40 - 80 years) a woman’s life, approximately 400 eggs will mature. 80 Diffres we Rrut Sses Menopause: - the termination of the AFAB reproductive years due to cessation of ovulation - Suggested that the higher incidence of genetic defects in children produced by older women can be linked to the age of the follicles. Older follicles are presumed to have a greater chance of genetic damage. Q - What is the name of the event leading to the ‘genetic damage’? - Because AFAB sex hormones are produced within the ovary, menopause marks the end of a AFAB’s reproductive life and signals a drop in the production of AFAB hormones. 81 Horl Fec & Mesti The hypothalamus and pituitary gland in the brain control the production of AFAB sex hormones (ie: estrogen and progesterone) in the ovaries. Gonadotropin-releasing hormone (GnRH) is produced by the hypothalamus. It stimulates the anterior pituitary gland to secrete and release the two gonadotropic hormones (gonadotropins), follicle-stimulating hormone (FSH) and luteinizing hormone (LH), at DIFFERENT TIMES in the menstrual cycle. 82 83 AF orl Fec on. Follicular Phase During the follicular phase of the menstrual cycle, the anterior pituitary releases FSH and follicle development is stimulated. - The follicles within the ovary secrete estrogen, which initiates the development of the endometrium. - As early estrogen levels rise, a negative feedback message is sent to the pituitary gland to turn off secretions of FSH. This ends the follicular phase of the menstrual cycle. 84 AF orl Fec on. Ovulation - At this point estrogen production cause a positive feedback loop - The rise in estrogen also stimulates the production of LH. - LH secretion rises dramatically and ovulation occurs. 85 AF orl Fec on. Luteal phase After ovulation, the remaining follicular cells, under the influence of LH, are transformed into a functioning corpus luteum, starting the luteal phase of the menstrual cycle. - Cells of the corpus luteum secrete both estrogen and progesterone. The buildup of estrogen and progesterone will further increase the development of the endometrium. - As progesterone and estrogen build up within the body, a second negative feedback mechanism is activated. Progesterone and estrogen work together to inhibit the release of both FSH and LH. - Without gonadotropic hormones, the corpus luteum begins to deteriorate, slowing estrogen and progesterone production. The drop in ovarian hormones signals the beginning of menstruation. 86 Note: - some birth control pills (also called oral contraceptives) contain high concentrations of progesterone, which inhibit ovulation and thereby prevent conception. Horl Siri & Diffres Recall that FSH and LH are also involved in regulation of the both reproductive systems. - Similarities between both systems extend beyond this. - For example, testosterone and estrogen can be produced in both systems - Secondary sex characteristics result because the levels of testosterone exceed the levels of estrogen in AMAB. - AMAB’s are ensured of maintaining low levels of estrogen by excreting them at an accelerated rate. 88 AFAB Q# 3-4 p 526 Q# 1-7 p 529 - Comt Bih r Mets Car - AF ors Gu Not Practice 90 Lab Inetin p 527-528 Practice 91 5. Ferza & Devme Human Reproduction & Development #5 Tod’ Obet - Trace the processes of fertilization, implantation and extra-embryonic membrane formation, i.e., placenta, amnion, chorion, allantois, followed by embryonic and fetal development, parturition and lactation, and describe the control mechanisms of these events, i.e., progesterone, LH, human chorionic gonadotropin (hCG), prostaglandins, oxytocin, prolactin. - Describe development from fertilization to parturition in the context of the main physiological events that occur in the development of organ systems during each major stage (trimester); i.e., zygote, blastocyst, gastrulation, general morphogenesis. - Identify major tissues and organs that arise from differentiation and morphological development of the ectoderm, mesoderm and endoderm in the embryo; i.e., - ectoderm: nervous system, epidermis. - mesoderm: skeleton, muscles, reproductive structures. - endoderm: lining of the digestive and respiratory systems, endocrine glands. - Describe the influence of environmental factors on embryonic and fetal development; e.g., maternal lifestyle, teratogens such as alcohol, drugs, viral infections and radiation. 93 Ferza, Pren & Bir The reproductive cycle of humans… - Recall cell reproduction - Diploid & haploid stages 94 Ferza Day 1 Fertilization in humans occurs in a Fallopian tube, and involves the union of a sperm cell with a secondary oocyte (not finished meiosis). The secondary oocyte then completes its development to become the fertilized ovum (zygote). The zygote receives 23 chromosomes from the sperm cell and 23 chromosomes from the oocyte, and so has 46 chromosomes. 95 Ferza Day 1-5 ot. Once a sperm has attached, the embedded oocyte membrane receptors change shape to discourage other sperm from attaching to another receptor on the egg’s membrane (this prevents interspecific fertilization) the acrosome of the sperm releases an enzyme (hyaluronidase), which digests a path through the corona radiata of the egg. Sperm may live 3-5 days in the the “naked” sperm is able to penetrate the zona pellucida AFAB body. -> inject chromosomal DNA It takes the fertilized ovum 3 to 5 days to reach the uterus. 96 Ferza Day 1-5 ot. During travel from Fallopian Tube to the Uterus: - Zygote undergoes many cell divisions in a process called cleavage. - Cleavage involves equal divisions of the cells of the zygote without any increase in size. - As a result, the cells of the zygote becomes progressively smaller with each division. Upon Reaching the uterus - Zygote has developed into a fluid-filled structure called a blastocyst. - Blastocyst consists of an outer sphere of cells, from which the extraembryonic structures develop, and an inner cell mass, from which the embryo develops. - Blastocyst attaches to the wall of the endometrium, a process referred to as implantation. 97 98 Ferza Day 5-7 Around days 5-7 after fertilization (conception), the embryo is called a blastocyst, “a hollow ball of cells” - consists of a ring of outer cells called the trophoblast (supporting cells) - clump of cells at one end inside (the inner cell mass which will become the embryo) 99 Ferza Day 5-7 The disk of cells at one end will form the baby The cavity is the blastocoel The outer layer of cells will form the chorion which will form the placenta, the exchange site between baby and mom. More on this in a bit... 100 Wha hs ar peny? Chas e Pgc i AF After ~4 Days the blastocyst transforms into an Embryo. - Will remain an Embryo until the eighth week of pregnancy → Now a Fetus Pregnancy takes place ~ 9 months from last menstrual period - Maintaining pregnancy requires stopping further menstruation But what about the hormone drop that cause menstrual shedding of the endometrium? 102 Chas Re. y. a Pran AF To prevent menstruation (ie: to maintain the endometrium): - Progesterone and estrogen levels must be maintained. - High levels of these hormones have a negative-feedback effect on the secretion of gonadotropic hormones. - LH levels must remain high to sustain the corpus luteum. - Should the corpus luteum deteriorate, the levels of estrogen and progesterone would drop, stimulating uterine contractions and the shedding of the endometrium. High levels of estrogen and progesterone, however, have a negative-feedback effect on the secretion of gonadotropic hormones like LH…so how is the endometrium maintained? This problem is avoided by the secretion of a hormone with a similar function to LH from the blastocyst itself. 103 Choic Hne Pci The outer layer of the blastocyst gives rise to two structures: - The chorion - The amnion. The chorion produces the hormone human chorionic gonadotropic hormone (hCG) (replacing LH), which maintains the corpus luteum for the first three months of pregnancy. The functioning corpus luteum continues producing progesterone and estrogen, which in turn maintain the endometrium. - The endometrium and embryo thus remain in the uterus. 104 Ami Dvem Between the amnion and the embryo or fetus is the amniotic cavity, a fluid-filled sac that insulates the embryo/fetus, protecting it from infection, dehydration, impact, and changes in temperature. - The extraembryonic coelom is a fluid-filled space between the amnion and the chorion. - By the second week of pregnancy, the yolk sac forms beneath the embryo. The yolk sac is the site of early red blood cell formation and later contributes to the primitive digestive tract (no nutritive function). 105 Plat Delen Cells from the chorion and endometrium combine to form the placenta, through which materials (ie: nutrients and wastes) are exchanged between the mother and fetus. At approximately the fourth month of pregnancy, the placenta begins to produce estrogen and progesterone. High levels of progesterone prevent further ovulation. This means that once a woman is pregnant, she cannot become pregnant again during that pregnancy. 106 Plat Delen Ct. The placenta is richly supplied with blood vessels. Projections called chorionic villi ensure that a large number of blood vessels of the fetus are exposed to maternal blood. - The allantois provides umbilical blood vessels in the placenta. However, unlike the chorion and amnion, the allantois does not envelop the fetus. - The placenta provides an interface for exchange between mother and fetus. – Nutrients and oxygen diffuse from the mother’s blood into the blood of the developing fetus. – Wastes diffuse in the opposite direction, moving from the fetus to the mother. - The umbilical cord connects the embryo with the placenta. 107 108 Q - umze fow ts: Ferza → Q - yohe s Alat: pota nun Ami: of lon Cho: pol w ec Yol : suc Plat: Practice 109 Emyo & Fta lon 1s Timr Nine months of pregnancy are divided into three trimesters. - The first trimester extends from fertilization to the end of the third month. - By the second week of development, the inner cells of the blastula have reorganized into a flattened disk made up of two layers. Gastrulation is the process in which the two-layered structure develops into a three-layered structure called a gastrula - Embryo is composed of 3 layers: ectoderm, mesoderm,endoderm. - Each of these three layers has a particular developmental fate as they will give rise to specific organs and structures in the fetus. 110 Gasli & Gr ar 111 Gasli n Gem s ot. Gastrulation begins when the disk elongates and forms a narrow line of cells at the midline. Cells migrate inward near this line and differentiate into the three layers of the gastrula. - The outer layer is the ectoderm - The middle layer is the mesoderm - The inner layer is the endoderm. By the end of the first month, many of the important organs and systems are beginning to develop. The four-chambered heart has formed, a large brain is visible, and limb buds with tiny fingers and toes have developed. By the ninth week, the embryo is referred to as a fetus. Arms and legs begin to move and a sucking reflex is evident. 112 S E ! THE A LL O W KN 113 114 115 Fet eln 2d Tis By the beginning of the second trimester (4th month – end of 6th month), all of the fetus’ organs have formed, although they are not fully developed. During this trimester, the organs continue to develop and the fetus increases in size. - Soft hair begins to cover the entire body. - By the sixth month, eyelids and eyelashes form. - Most of the cartilage that formed the skeleton has been replaced by bone cells. Should the mother go into labour at the end of the second trimester, there is a chance that the fetus will survive. It will move enough to make itself known to the parent and it begins to look more like a human infant. 116 Fet eln 3d Tis During the third trimester (7th month – birth), the baby grows rapidly. Organ systems have been established during the first two trimesters All that remains is for the body mass to increase and the organs to enlarge and become more developed. 117 118 Q - Usi t rid le m u t/sis ce a sl el o mta dopt mite f h es in h 2 & 3r tiss. Practice 119 Fet eln & Se tino The principal gene for sex determination is found on the Y chromosome. The SRY (Sex-determining Region of the Y chromosome) gene is mainly responsible for determining the AMAB phenotype in humans. - A fetus does not differentiate until the sixth or seventh week of pregnancy. - In the presence of the SRY gene, the developing gonads become testis due to TDF (testis determining factor) - Synthesis of hormones by cells of the testis subsequently directs the development of sex characteristics. - Testes develop inside the body cavity in the same location as the ovaries and gradually descend 120 EXES - R en Clion [li] Mutations and translocation errors of replication on the SRY (Sex-determining Region of the Y chromosome) gene can result different conditions in humans. SRY Mutations Translocations - 46,XY complete gonadal - 46,XY disorder of sex - 46,XX testicular disorder of sex dysgenesis development development - 46,XY pure gonadal - partial gonadal dysgenesis - random event during the formation dysgenesis of sperm cells AKA - Swyer Syndrome Ambiguous presentation of XX fetus with an X chromosome that XY Fetus with underdeveloped or genitalia and/or other related carries the SRY gene will develop sex undeveloped testes symptoms characteristics consistent with development of testis 121 Fet eln & Se tino The balance between human sex differentiation is also determined by the hormones circulating in the bloodstream. - AFAB produce some AMAB sex hormones or androgens, along with estrogen. - AFAB bodies will synthesize estrogen from androgens such as testosterone. - AMAB produce AFAB sex hormones, but in much smaller quantities by comparison. At no time is the hormonal balance between sex determining hormones more critical than during fetal development. Excessive estrogen at the delicate time can transform an organism with XY genes into what outwardly appears to be a XX. Conversely, an overabundance of androgens or XY sex hormones during fetal development can produce the sex organs of a XY in the genetic body of a XX. 122 Effec f Eron Ages Emyo/Fet eln The dependency of a newborn on its parents provides a special relationship. However, the dependency prior to birth is even greater. The health and lifestyle decisions of the carrier remain with the child for a lifetime. Proper nutrition and prenatal vitamins prevent many developmental problems. - Folic Acid is proven to reduce the chances of neural tube defects during gastrulation. Like spina bifida (a spinal cord defect) and anencephaly (a brain defect). Agents (chemicals and microbes) that are capable of causing developmental abnormalities in utero are called teratogens. - A number of drugs that can cross the placental membrane have been suspected of adversely affecting fetal development. - Most teratogens cause problems early in fetal development. Some organ systems, such as the nervous system, are sensitive to teratogens very early during pregnancy. 123 Effec f Fa All Sdo (FA) Occurs when a mother drinks alcohol while she is pregnant in the first trimester. FAS is a spectrum disorder lead to a wide variety of symptoms in affected individuals (4% of Canadians) These challenges may look like: - being impulsive - not understanding consequences - being unfocused and easily distracted - difficulties keeping up with classroom learning - challenges handling money - challenges learning how to tell time - forgetting how to do something they’ve done before - having trouble staying organized and planning ahead 124 Effec f Fa All Sdo (FA) A recent canadian study found that 10% of criminal offenders were diagnosed with an FASD, while a diagnosis could not be confirmed or ruled out in 15% of offenders. Neuropsychological deficits unrelated to prenatal alcohol exposure were found in 45% of offenders, and 30% were found to have no identifiable deficits. 125 Effec f Cab Csut “The use of cannabis during pregnancy could produce neurochemical alterations both in humans and in research animals.” [link] - Compounds can readily cross the placental barrier - Be aware of risks of using cannabis during pregnancy in order to minimize the possible consequences - Mainly include affective disorders and ADHD and which depend on duration and intensity of the prenatal exposure. Roncero, C., et al. Cannabis use during pregnancy (2020) 126 127 Q - o l me n h a pna n fir tis? Q - ow s e my a h me? Q - ha hen, n em fa dopt, ha fis tis? Q - ha t or co t it se t penle (FA) sdo? Q - ha t ik ut of ra ces ceon ban rer to l elen? Practice 128 “ “There will never be a day, like the day your baby was born” Some Internet Meme 129 Parti (AK ir) Approximately 266 days after implantation, uterine contractions signal the beginning of parturition - the act of giving birth; labour 130 Parti (AK ir) co. The cervix thins and begins to dilate. As the amnion is forced into the birth canal, it often bursts, and amniotic fluid lubricates the canal. - referred to as the “breaking of the water” As the cervix dilates, uterine contractions move the baby through the birth canal. Following the birth of the baby, the placenta is also delivered (the “after-birth”). 131 Parti (AK ir) co. Baby moves from a world of darkness to light. World of constant temperature of 37oC to room temperature of 20-22oC. Aquatic world to dry air (terrestrial) World of food and oxygen supplied by the placenta to the need of a digestive and respiratory system World of waste removal by the placenta to the need of a digestive, urinary and respiratory system. Wouldn’t you be upset? 132 Parti & Hmo Hormones play a vital role in the birthing process: - Relaxin, a hormone produced by the placenta prior to labour, causes the ligaments within the pelvis to loosen and the cervix to soften, providing a more flexible passageway for the baby during delivery. - Although the mechanism is not completely understood, it is believed that a decreased production progesterone is crucial to the onset of labour. - Oxytocin, a hormone from the posterior pituitary gland, causes strong uterine contractions. - Prostaglandins, which are also believed to trigger strong uterine contractions, appear in the carrier’s blood prior to labour. - Labour can be induced by administering prostaglandins or pitocin, which is a synthetic form of the hormone oxytocin. 133 Lacon Breast development is stimulated from the onset of puberty by estrogen and progesterone. - During pregnancy, elevated levels of estrogen and progesterone prepare the breasts for milk production (lactation). - A hormone called prolactin, produced by the anterior pituitary gland, is responsible for stimulating glands within the breast to begin producing fluids. - Estrogen stimulates the release of large amounts of prolactin during pregnancy; - milk production does not occur before birth because the action of prolactin is inhibited by the high levels of progesterone 134 Lacon t. The drop in estrogen and progesterone levels after birth results in decreased amounts of prolactin, but an increase in prolactin activity because the progesterone-induced inhibition is relieved. Prolactin initially causes the production of colostrum, a fluid that closely resembles breast milk. Colostrum contains milk sugar and milk proteins, but lacks the milk fats found in breast milk. A few days after birth, prolactin stimulates the production of milk. Colostrum and then the milk, supply the baby with an important source of antibodies. 135 Although prolactin increases milk production, the milk does not flow easily. Milk produced in the lobes of glandular tissue must be forced into the ducts that lead to the nipple. 1. The suckling action of the newborn stimulates nerve endings in the areola of the breast. 2. Sensory nerves carry information to the pituitary gland, causing the release of oxytocin. 3. Within the breast, oxytocin causes weak contractions of smooth muscle, forcing milk into the ducts. 4. More infant suckling 5. Within the uterus, oxytocin causes weak contractions of smooth muscle, allowing the uterus to slowly return to its pre-pregnancy size and shape. 136 137 Q#1 on . 532. Q# 2 an 3 p. 536. Q# 1 – 5 on . 544. Practice 138 6. Tecl an Pgc Human Reproduction & Development #6 Tod’ Obet - Describe the physiological or mechanical basis of different reproductive technologies; i.e., conception control, in vitro fertilization, infertility reversal. 140 Tecli Asit it Pgc (IVF) Fertility Artificial (CVS) In vitro Drugs Insemination Amniocentesis Chorionic Fertilization Villus Sampling (AFP) RH Umbilical Ultrasound Alpha - Incompatibility Genetic Cord Stem fetoprotein Counseling Cells testing In Vi rizi (IV) In vitro fertilization involves removing eggs from the ovaries, fertilizing them in the laboratory and then replacing the embryos into the uterus where they implant and mature. They successfully delivered Louise Brown in 1978, the world's first ‘test tube baby’ In Vi rizi (IV) co. Various hormone medications are administered in the treatment cycle. Their purpose is to: - Enhance the growth and maturation of several follicles, thereby improving chances for fertilization - Control the timing of ovulation so eggs can be retrieved before they are spontaneously released In Vi rizi (IV) co. National Rates of Singleton, Twin, and Triplet and Higher-Order Live Births Resulting from IVF, 1997–2011. [ link ] Multiple pregnancies are the most common complication occurring in about 20% of IVF cases, since more than one embryo is usually implanted. Fert Dug Used to stimulate follicle production in interested parents. It increases the number of eggs or sperm produced. Clomiphene citrate Often used prior to IVF to stimulate egg development.
