Human Body Systems Semester 2 Year 1 Reproduction

Front 1

What is the function of the scrotum and the cremaster and dartos muscles?

Back 1

The location of the scrotum and the contraction of its muscle fibres regulate the temperature of the testes. Normal sperm production requires a temperature about 2-3 degrees C below core body temperature. This lowered temperature is maintained within the scrotum because it is outside the pelvic cavity. In response to cold temperatures the cremaster and dartos muscles contract. Contraction of the cremaster muscles moves the testes closer to the body where they can absorb the heat. Contraction of the dartos muscle causes the scrotum to become tight which reduces heat loss. Exposure to warmth reverses these actions.

Front 2

Describe the structure of the testes.

Back 2

The testes or testicles are paired oval glands in the scrotum measuring about 5cm long and 2.5cm in diameter. A serous membrane called the tunica vaginalis partially covers the testes. Internal to the tunica vaginalis is a dense white fibrous capsule composed of dense irregular connective tissue, the tunica albuginea. It extends inward forming septa that divide testis into internal compartments called lobules. Each of the 200-300 lobules contains one to three tightly coiled seminiferous tubules where sperm are produced. The process by which the seminiferous tubules of the testes produce sperm is called spermatogenesis.

Front 3

Where in the testes are sperm produced?

Back 3

The seminiferous tubules contain two types of cells; spermatogenic cells which are the sperm-forming cells and Sertoli cells. Stem cells called spermatogonia are spermatogenic cells that remain dormant during childhood and actively begin producing sperm at puberty. Toward the lumen of the seminiferous tubule are layers of progressively more mature spermatogenic cells. In order of advancing maturity these are primary spermatocytes, secondary spermatocytes, spermatids and sperm. After a sperm cell, or spermatozoon has formed it is released into the lumen of the seminiferous tubule.

Front 4

What are the functions of the Sertoli and Leydig cells and where in the testes are they located?

Back 4

Among the spermatogenic cells in the seminiferous tubules, Sertoli cells extend from the basement membrane to the lumen of the tubule. Internal to the basement membrane and spermatogonia, tight junctions join neighbouring Sertoli cells to one another. These junctions form an obstruction known as the blood-testis barrier because substances must first pass through the Sertoli cells before they can reach the developing sperm. By isolating the developing gametes from the blood the blood-testis barrier prevents an immune response against the spermatogenic cell's surface antigens which are recognized as foreign by the immune system. The blood-testis barrier does not include spermatogonia. Sertoli cells support and protect developing spermatogenic cells in several ways. They nourish spermatocytes, spermatids and sperm, phagocytize excess spermatid cytoplasm as development proceeds and control movements of spermatogenic cells and the release of sperm into the lumen of the seminiferous tubule. Sertoli cells also produce fluid for sperm transport and secrete the hormone inhibin to decrease the rate of spermatogenesis. In the spaces between adjacent seminiferous tubules are clusters of cells called Leydig cells. These cells secrete testosterone the most prevalent androgen.

Front 5

How does anaphase I of meiosis differ from anaphase of mitosis and anaphase II of meiosis?

Back 5

Anaphase I of meiosis is where the homologous chromosomes separate but sister chromatids remain together. Anaphase in meiosis and anaphase II of meiosis is where sister chromatids separate.

Front 6

What is the significance of meiosis I?

Back 6

In meiosis I homologous pairs of chromosomes line up at the metaphase plate and crossing over occurs to rearrange genes between chromatids. Then the meiotic spindle pulls one chromosome of each pair to an opposite pole of the dividing cell. The two cells formed by meiosis I are called secondary spermatocytes. Each secondary spermatocyte has 23 chromosomes, the haploid number. However after meiosis I each chromosome within a secondary spermatocyte is made of two chromatids still attached by a centromere.

Front 7

Describe the process of spermatogenesis including the final stage spermiogenesis.

Back 7

In humans spermatogenesis takes 65-75 days. It begins with the spermatogonia which contain the diploid number (2n) number of chromosomes. When spermatogonia undergo mitosis some spermatogonia remain near the basement membrane of the seminiferous tubule in an undifferentiated state to serve as a reservoir of cells for future sperm production. The rest of the spermatogonia lose contact with the basement membrane, squeeze through the blood-testis barrier, undergo developmental changes and differentiate into primary spermatocytes. Primary spermatocytes like spermatogonia are diploid ie they have 46 chromosomes. Shortly after it forms each primary spermatocyte replicates its DNA and then meiosis begins. In meiosis I, homologous pairs of chromosomes line up at the metaphase plate and cross-over occurs to rearrange genes between chromatids. Then the meiotic spindle pulls one chromosome of each pair to an opposite pole of the dividing cell. The two cells formed by meiosis I are called secondary spermatocytes. Each secondary spermatocyte has 23 chromosomes, the haploid number. However, after meiosis I each chromosome within a secondary spermatocyte is made up of two chromatids (2 copies of the DNA) still attached by a centromere. In meiosis II the chromosomes line up in single file along the metaphase plate and the two chromatids of each chromosome separate. The four haploid cells resulting from meiosis II are called spermatids. Therefore a single primary spermatocyte with 46 chromosomes undergoes two rounds of cell division in meiosis I and meiosis II to produce four spermatids each with 23 chromosomes. A unique process occurs during spermatogenesis. As spermatogenic cells proliferate they fail to complete cytoplasmic separation (cytokinesis). The four daughter cells remain in contact via cytoplasmic bridges through their entire development. This pattern of development most likely accounts for the synchronized production of sperm in any given area of a seminiferous tubule. It may also have survival value in that half of the sperm contain an X chromosome and half contain a Y chromosome. The larger X chromosome may carry genes needed for spermatogenesis that are lacking on the smaller Y chromosome. The final stage of spermatogenesis, spermiogenesis is the development of haploid spermatids into sperm. No cell division occurs in spermiogenesis. Each spherical haploid spermatid becomes an elongated slender sperm cell.

Front 8

What are the functions of the sperm cell acrosome and middle piece?

Back 8

An acrosome which covers the anterior two-thirds of the nucleus forms atop the condensed elongated nucleus. It is a caplike vesicle filled with enzymes that help a sperm cell penetrate a secondary oocyte to bring about fertilization. The middle piece contains mitochondria arranged in a spiral which provides the energy (ATP) for locomotion of sperm to the secondary oocyte and for sperm metabolism.

Front 9

Describe the hormonal control of spermatogenesis and testosterone secretion.

Back 9

At the onset of puberty the hypothalamus increases its secretion of gonadotropin-releasing hormone (GnRH). This hormone in turn stimulates the anterior pituitary to increase its secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Luteinizing hormone stimulates Leydig cells which are located between seminiferous tubules to secrete the hormone testosterone. This steroid hormone is synthesized from cholesterol in the testes and is the principal androgen. Through negative feedback, testosterone suppresses secretion of luteinizing hormone by the anterior pituitary and suppresses secretion of gonadotropin-releasing hormone by the hypothalamus. In some target cells such as those in the prostate, testosterone is converted to another androgen called dihydrotestosterone (DHT). Follicle stimulating hormone acts indirectly to stimulate spermatogenesis. Follicle stimulating hormone and testosterone act synergistically on the Sertoli cells to stimulate secretin of androgen-binding protein (ABP) into the lumen of the seminiferous tubules and into the interstitial fluid around the spermatogenic cells. Androgen-binding protein binds to testosterone keeping its concentration high. Testosterone stimulates the final steps of spermatogenesis in the seminiferous tubules. Once the degree of spermatogenesis required for male reproductive functions has been achieved, Sertoli cells release inhibin a hormone named for its role in inhibiting follicle stimulating hormone secretion by the anterior pituitary. If spermatogenesis is proceeding too slowly, less inhibin is released which permits more follicle stimulating hormone secretion and an increased rate of spermatogenesis.

Front 10

What are the functions of testosterone?

Back 10

Testosterone and dihydrotestosterone both bind to the same androgen receptors within the nuclei of target cells. The hormone receptor complex turns some genes on and turns others off. Testosterone produces several effect such as prenatal development, the development of male sexual characteristics, the development of sexual function and the stimulation of anabolism.

Front 11

List the components of the duct system of the male reproductive system in order from testes to urethra.

Back 11

The ducts of the testis, the epididymis, the ductus deferens, the spermatic cord, the ejaculatory ducts and the urethra.

Front 12

Name the structures in the spermatic cord.

Back 12

The spermatic cord contains the ductus deferens, the testicular artery, veins, autonomic nerves, lymphatic vessels and the cremaster muscle.

Front 13

Describe the entry of the spermatic cord through the abdominal wall.

Back 13

The spermatic cord passes through the inguinal canal, an oblique passageway in the anterior abdominal wall that ends at the superficial inguinal ring, an opening in the aponeurosis of the external oblique muscle.

Front 14

What are the three subdivisions of the male urethra?

Back 14

The prostatic urethra passes through the prostate. As this duct continues inferiorly it passes through the deep muscles of the perineum where it is known as the membranous urethra. As the duct passes through the corpus spongiosum of the penis it is known as the spongy urethra or penile urethra.

Front 15

Describe the locations and functions of the accessory sex glands.

Back 15

The ducts of the male reproductive system store and transport sperm but the accessory sex glands secrete most of the liquid portion of semen that protects semen and facilitates their movement. The accessory sex glands include the seminal vesicles, the prostate and the bulbourethral glands. The alkaline nature of the seminal fluid helps to neutralize the acidic environment of the male urethra and female reproductive tract that otherwise would inactivate and kill sperm. Prostaglandins contribute to sperm motility and viability and may stimulate smooth muscle contractions within the female reproductive tract. The clotting proteins help semen coagulate after ejaculation. The prostate secretes a slightly acidic fluid that contains citric acid used by sperm for ATP production, proteolytic enzymes that eventually break down the clotting proteins from the seminal vesicles and seminalplasmin which is an antibiotic that may help decrease the number of naturally occurring bacteria in semen and in the lower female reproductive tract. During sexual arousal the bulbourethral glands secrete an alkaline fluid into the urethra that protects the passing sperm by neutralizing acids from urine in the urethra. They also secrete mucous that lubricates the end of the penis and the lining of the urethra decreasing the number of sperm damaged during ejaculation.

Front 16

Which accessory sex gland contributes the majority of seminal fluid?

Back 16

The seminal vesicles.

Front 17

Which tissue masses form the erectile tissue in the penis and how do they become rigid during sexual arousal?

Back 17

Erectile tissue is composed of numerous blood sinuses (vascular spaces) surrounded by smooth muscle and elastic connective tissue. The combination of increased blood flow and widening of the blood sinuses results in an erection.

Front 18

Which tissue mass keeps the urethra open during ejaculation?

Back 18

The smaller midventral mass, the corpus spongiosum penis, contains the spongy urethra and keeps it open during ejaculation.

Front 19

Explain the physiological processes involved in ejaculation.

Back 19

In a sympathetic reflex, the smooth muscle sphincter at the base of the urinary bladder closes, peristaltic waves occur in the ducts of the male and semen is propelled into and through the male urethra.

Front 20

What are the functions of the ovaries?

Back 20

To produce gametes and hormones.

Front 21

How are they held in place in the pelvic cavity?

Back 21

By the broad ligament, mesovarium, ovarian ligament and the suspensory ligament.

Front 22

Which structures in the ovary serve an endocrine function and which hormones do they secrete?

Back 22

Follicles which produce oestrogens and corpus luteum which produces oestrogens and progesterone.

Front 23

How does the age of a primary oocyte in a female compare with the age of a primary spermatocyte in a male?

Back 23

Primary oocytes are present before birth whereas primary spermatocytes develop during puberty.

Front 24

From which follicle does ovulation occur?

Back 24

A mature follicle.

Front 25

Relate meiosis I and meiosis II to the development of follicles during oogenesis and after ovulation.

Back 25

During fetal development, meiosis I begins. After puberty primary oocytes complete meiosis I which produces a secondary oocyte and a first polar body that may or may not divide again. The secondary oocyte begin meiosis II. A secondary oocyte and first polar body is ovulated. After penetration, meiosis II resumes. The oocyte splits into an ovum and a second polar body.

Front 26

Where are the uterine tubes located?

Back 26

The uterine tubes extend laterally from the uterus and lie between the folds of the broad ligaments of the uterus.

Front 27

What are the functions of the cells that line the uterine tubes?

Back 27

The ciliated simple columnar cells function to help move a fertilized ovum along the tube toward the uterus. Nonciliated cells with microvilli secrete a fluid that provides nutrition for the ovum.

Front 28

What are the principal parts of the uterus?

Back 28

The fundus, body and cervix.

Front 29

How is the uterus held in its normal position in the pelvic cavity?

Back 29

Broad ligaments attach the uterus to either side of the pelvic cavity. Uterosacral ligaments lie on either side of the rectum and connect the uterus to the sacrum. Cardinal ligaments extend from the cervix and vagina to the lateral pelvic wall. Round ligaments extend between the layers of the broad ligament from the uterus just inferior to the uterine tubes to the labia majora of the external genitalia.

Front 30

Which of the structural features of the endometrium and myometrium contribute to their function?

Back 30

The endometrium has two layers. The stratum basalis which is permanent and gives rise to a new stratum functionalis after each menstruation. The stratum functionalis lines the uterine cavity and sloughs off during menstruation. Myometrium consists of three layers of smooth muscle fibres that function in labour and childbirth.

Front 31

What are the functions of the vagina?

Back 31

A receptacle for the penis during sexual intercourse, an outlet for menstrual flow and a passageway for childbirth.

Front 32

What structures comprise the vulva?

Back 32

The mons pubis cushions the pubic symphysis. The labia majora protectively encloses the medial components of the vulva. The labia minora contains sebaceous glands. The clitoris is capable of enlargement upon tactile stimulation and has a role in sexual excitement in the female. The vestibule contains the hymen, vaginal orifice, external urethral orifice and openings of the ducts of several glands. The bulb of the vestibule consists of two elongated masses of erectile tissue which become engorged with blood during sexual arousal resulting in narrowing the vaginal orifice and placing pressure on the penis during intercourse.

Front 33

Which structures in males are homologous to the ovaries, the clitoris, the greater vestibular glands and the bulb of the vestibule?

Back 33

The ovaries are equivalent to the testes. The clitoris is equivalent to the glans penis. The greater vestibular glands are equivalent to the bulbourethral glands. The bulb of the vestibule is equivalent to the corpus spongiosum penis and the bulb of the penis.

Front 34

Which surface structures are anterior to the vaginal opening?

Back 34

The external urethral orifice, the clitoris and the mons pubis.

Front 35

Which surface structures are lateral to the vaginal opening?

Back 35

The labia majora and labia minora.

Front 36

How are breasts supported?

Back 36

By strands of connective tissue called the suspensory ligaments of the breast.

Front 37

Through which structure does milk pass from its production site to its exit from the breast?

Back 37

From the alveoli to secondary tubules to mammary ducts to lactiferous sinuses to lactiferous ducts to the exterior.

Front 38

Which hormones regulate the synthesis and ejection of milk?

Back 38

Oxytocin and prolactin.

Front 39

Which hypothalamic and anterior pituitary hormones control the ovarian and uterine cycles?

Back 39

Gonadotropin-releasing hormone secreted by the hypothalamus. Follicle-stimulating hormone and luteinizing hormone from the anterior pituitary.

Front 40

Which oestrogen exerts the major effect in non-pregnant females?

Back 40

Estradiol

Front 41

What effects do follicle stimulating hormone and luteinizing hormone have on the follicles?

Back 41

Follicle-stimulating hormone initiates growth of the ovarian follicles while luteinizing hormone stimulates their further development..

Front 42

What are the effects of oestrogen, progesterone, relaxin and inhibin in the female reproductive cycle?

Back 42

Oestrogen promotes uterine lining development and development of the mature follicle. Progesterone promotes development of the uterine lining and maintains the lining if pregnancy occurs. Inhibin inhibits follicle stimulating hormone and luteinizing hormone secretion. Relaxin relaxes the uterus.

Front 43

What effects does oestrogen have outside the uterus?

Back 43

Oestrogen promotes the development and maintenance of female reproductive structures, secondary sex characteristics and the breasts. It works synergistically with human growth hormone to increase protein anabolism including the building of strong bones and lowers blood cholesterol.

Front 44

List the phases of the female reproductive cycle?

Back 44

The menstrual phase, the preovulatory phase, ovulation, the postovulatory phase

Front 45

List the phases of the ovarian cycle?

Back 45

Primordial follicles develop, the dominant follicle appears and becomes the mature follicle, after ovulation the mature follicle collapses.

Front 46

List the phases of the uterine cycle?

Back 46

The entire stratum functionalis sloughs off and the stratum functionalis undergoes renewal

Front 47

Why does only one follicle usually become a mature follicle?

Back 47

A follicle that begins to develop at the beginning of a particular menstrual cycle may not reach maturity and ovulate until several menstrual cycles later since the developmental process may take several months to occur.

Front 48

Which hormones are responsible for the proliferative phase of endometrial growth, ovulation, the growth of the corpus luteum and the surge of luteinizing hormone at midcycle?

Back 48

Hormones responsible for endometrial growth are oestrogens. The hormones responsible for ovulation are oestrogens, luteinizing hormone and gonadotropin-releasing hormone. The hormones responsible for the growth of the corpus luteum are luteinizing hormone and the hormones responsible for the surge of luteinizing hormone at midcycle are oestrogens.

Front 49

Is stimulation of gonadotropin-releasing hormone by declining levels of oestrogens and progesterone a positive or negative feedback effect? Explain your answer.

Back 49

It is negative feedback.

Front 50

What causes follicles to start growing again in a new ovarian cycle?

Back 50

Decreased levels of progesterone, oestrogens and inhibin result in the release of gonadotropin-releasing hormone, follicle stimulating hormone and luteinizing hormone which results in follicles starting to grow again.

Front 51

What mechanisms move sperm from the vagina to the uterine tube?

Back 51

Sperm flagella movement and contractions of the walls of the uterus and uterine tube.

Front 52

How does sperm penetrate the covering of the secondary oocyte?

Back 52

Sperm receptors in the zona pellucida bind to specific membrane proteins in the sperm head triggering the release of sperm acrosomal enzymes that digest a path through the zona pellucida as the lashing sperm tail pushes the sperm cell onward.

Front 53

How is polyspermy prevented?

Back 53

The fast way to block polyspermy is that the oocyte cell membrane depolarizes on fertilization. A slow block to polyspermy is when intracellular calcium ions are released that stimulate exocytosis of chemicals which inactivate sperm receptors and harden the entire zona pellucida.

Front 54

What is a morula and how is it formed?

Back 54

A morula is a solid sphere of cells formed by the mitotic divisions of the zygote.

Front 55

Describe the layers of the blastocyst and their eventual fates.

Back 55

The inner cell mass forms the embryoblast which forms the embryo. The trophoblast forms the foetal portion of the placenta.

Front 56

In which phase of the uterine cycle does implantation occur? Where does it usually occur? How is the blastocyst oriented at implantation?

Back 56

Implantation occurs in the postovulatory phase. Implantation usually occurs in the fundus or body of the uterus. The blastocyst is oriented toward the endometrium.

Front 57

What is the decidua? What are the components of the decidua? Which part of the decidua helps form the maternal part of the placenta?

Back 57

The decidua basalis is the portion of the endometrium between the embryo and the stratum basalis. The decidua capsularis is the portion of the endometrium located between the embryo and the uterine cavity. The decidua parietalis is the remaining modified endometrium that lines the noninvolved areas of the rest of the uterus. The decidua basalis helps form the maternal part of the placenta.

Front 58

How does the embryo burrow into the endometrium?

Back 58

Syncytiotrophoblast cells secrete enzymes that enable the blastocyst to penetrate the uterine lining by digesting and liquefying the endometrial cells.

Front 59

How is the bilaminar embryonic disc formed? How is it connected to the trophoblast?

Back 59

The bilaminar embryonic disc is formed by differentiation of the embryoblast cells into hypoblast and epiblast cells that form a flat disc. It is connected to the trophoblast by a band of extraembryonic mesoderm called the connection stalk.

Front 60

Describe the structure of the placenta. What is the importance of the placenta?

Back 60

The structure is formed by the foetal portion formed by the chorionic villi of the chorion and the maternal portion is formed by the decidua basalis of the endometrium. The placenta allows oxygen and nutrients to diffuse from maternal blood into foetal blood while carbon dioxide and wastes diffuse from foetal blood into maternal blood. It is a protective barrier against most microorganisms, stores nutrients which are released into foetal circulation as required and produces hormones needed to sustain the pregnancy.

Front 61

Describe the components of the umbilical cord.

Back 61

The components of the umbilical cord are two umbilical arteries, one umbilical vein and supporting mucous connective tissue.

Front 62

What is the afterbirth?

Back 62

Afterbirth is the placenta detached from the uterus.

Front 63

What is the source of progesterone and oestrogens during early pregnancy? During late pregnancy?

Back 63

The corpeus luteum is the source of progesterone and oestrogen during early pregnancy. The placenta is the source of progesterone and oestrogen during late pregnancy.

Front 64

What is the source and function of human chorionic gonadotropin? Of human chorionic somatomammotropin?

Back 64

The source of human chorionic gonadotropin is chorion. Its function is to stimulate the corpeus luteum to continue production of progesterone and oestrogens. The source of human chorionic of somatomammotropin is chorion. Its function is to help prepare the mammary glands for lactation, enhance maternal growth by increasing protein synthesis and regulate certain aspects of metabolism in both mother and foetus.

Front 65

Which hormone helps ease the delivery of the baby? How?

Back 65

Relaxin by increasing the flexibility of pelvic ligaments and helping dilate the uterine cervix during labour.

Front 66

Which hormone helps control when birth occurs?

Back 66

Corticotropin-releasing hormone

Front 67

Which hormonal changes induce labour?

Back 67

Hormonal changes that induce labour are a rise in oestrogen levels, release of oxytocin accompanied by an increase in oxytocin receptors, release of prostaglandins and an increase in relaxin.

Front 68

Which hormone controls labour contractions? Why is control of labour considered a positive feedback loop?

Back 68

Oxytocin control labour contractions. It is a positive feedback loop because the actual birth process works to increase the levels of oxytocin with oxytocin levels falling only after the birth of the child.

Front 69

Which hormones contribute to lactation? What is the function of each?

Back 69

Prolactin and oxytocin. Prolactin contributes to milk synthesis. Oxytocin contributes to milk ejection.

Front 70

What are the advantages of breast-feeding over bottle feeding?

Back 70

The presence of beneficial cells for the infant, the presence of beneficial molecules in breast milk, decreased incidence of diseases in later life, support of optimal infant growth, enhancement of intellectual and neurological development as well as other benefits.

Front 71

What is the function of oxytocin other than its involvement in lactation?

Back 71

It helps bonding between mother and child.

Front 72

Male Reproductive System, what is a?

Back 72

a. Prostate

Front 73

Male Reproductive System, what letter is the prostate?

Back 73

a

Front 74

Male Reproductive System, what is b?

Back 74

b. Ejaculatory duct

Front 75

Male Reproductive System, what letter is the ejaculatory duct?

Back 75

b

Front 76

Male Reproductive System, what is c?

Back 76

c. Scrotum

Front 77

Male Reproductive System, what letter is the scrotum?

Back 77

c

Front 78

Male Reproductive System, what is d?

Back 78

d. Epididymus

Front 79

Male Reproductive System, what letter is the epididymus?

Back 79

d

Front 80

Male Reproductive System, what is e?

Back 80

e. Body of penis

Front 81

Male Reproductive System, what letter is the body of the penis?

Back 81

e

Front 82

Male Reproductive System, what is f?

Back 82

f. Ductus deferens

Front 83

Male Reproductive System, what letter is the ductus deferens?

Back 83

f

Front 84

Male Reproductive System, what is g?

Back 84

g. Testis

Front 85

Male Reproductive System, what letter is the testis?

Back 85

g

Front 86

Male Reproductive System, what is h?

Back 86

h. Prepuce

Front 87

Male Reproductive System, what letter is the prepuce?

Back 87

h

Front 88

Male Reproductive System, what is i?

Back 88

i. Glans penis

Front 89

Male Reproductive System, what letter is the glans penis?

Back 89

i

Front 90

Male Reproductive System, what is j?

Back 90

j. Corpus cavernosum penis

Front 91

Male Reproductive System, what letter is the corpus cavernosum penis?

Back 91

j