Biology 4.1

Question 1

Primary sex characteristics

Answer 1

Directly involved with reproduction, uterus and ovaries, testes

Question 2

Secondary sex characteristics

Answer 2

Sexual maturity, body hair, breasts, low voice, ass

Question 3

Male anatomy

Answer 3

Consists of testis, epididymis, vas deferent, penis, seminiferous vesicles, prostate gland, bulbourethral glands (Cowper’s glands)

Question 4

Testis

Answer 4

Oval shaped organ in scrotum, composed of a series of small convoluted tubules called seminiferous tubules that are separated by interstitial/ Leydig eggs, spermatogenesis and androgen/testosterone production occurs, 2-4 digress Celsius colder than rest of the body

Question 5

Epididymis

Answer 5

Coiled tube attached to each testis, sperm undergoes maturity here and are stored under ejaculation

Question 6

Vas deferens

Answer 6

duct that transfers sperm from epididymis to urethra

Question 7

Penis

Answer 7

has urethra to pee and for sperm

Question 8

Seminiferous vesicles

Answer 8

Accessory glands that do not come in to contact with sperm, secrete substances to aid in ejaculation

• mucus - secreted into vas deferens during ejaculation providing liquid medium for sperm
• fructose - provides energy to sperm
• prostaglandins - secreted to stimulate urethral contractions, allowing sperm to effectively move into uterus

Question 9

Prostate gland

Answer 9

No contact with sperm, secretes alkaline fluid to neutralize acidity of vagina and leftover urine in urethra

Question 10

Bulbourethral glands (Cowper’s glands)

Answer 10

Secretes viscous fluid to clean and lubricate urethra

Question 11

Spermatogenesis aka gamete production

Answer 11

Spermatogonia stem cells at basement membrane of seminiferous tubules undergo many mitosis cycles to make primary spermatocytes. Primary spermatocytes travel to lumen of seminiferous tubules and undergo meiosis I to make 2 secondary spermatocytes, then undergo meiosis II to make a total of 4 spermatids. Sertoli cells give nourishment for spermatid maturation. Mature spermatids called spermatozoa (male gametes, haploid, n=23) are stored in epididymis. During ejaculation, spermatozoa goes from epididymis to vas deferences to urethra

Question 12

Sperm

Answer 12

Consists of head, neck and tail

Question 13

Head of sperm

Answer 13

Has haploid nucleus and acrosome. Acrosome is a cap on anterior of spermatozoa which has enzymes to penetrate outside layer of ovum, derived from Golgi apparatus

Question 14

Neck of sperm

Answer 14

Midpiece, has mitochondria

Question 15

Tail of sperm

Answer 15

flagellum, long structure that beats to allow for mobility of spermatozoa

Question 16

Male hormones

Answer 16

GnRH (gonadotropin releasing hormone) is made and secreted by hypothalamus to the portal blood system, this brings GnRH directly to anterior pituitary gland which releases FSH (follicle stimulating hormone) and LH (Leutenizing hormone). FSH and LH circulate and reach the testes where LH stimulates interstitial cells to make testosterone and other androgens. FSH and LH both stimulate Sertoli cells to indirectly promote spermatogenesis

Question 17

Female anatomy

Answer 17

Ovary, oviduct (Fallopian tubes), uterus, cervix and vagina

Question 18

Ovary

Answer 18

Small, almond-shaped organs where female gametes called ovum are made and stored until maturation

Question 19

Oviduct (Fallopian tubes)

Answer 19

Tubular structure connecting ovaries to uterus, mature ovum housed here until fertilized, fertilized ovum travel through oviduct to uterus, oviduct lined with brush-like border projections that sweep zygote to uterus for implantation

Question 20

Uterus

Answer 20

Lined with blood cells called the endometrium during specific phases, fertilized ovum implants itself on uterine wall, embryo develops here

Question 21

Cervix and vagina

Answer 21

Cervix connects uterus to vagina, sperm is ejaculated into vagina and must pass through cervix, to uterus/oviduct to fertilize ovum

Question 22

Oogenesis aka female gametogenesis

Answer 22

Ova production occurs during embryonic development before birth. In ovaries, oogonia cells undergo mitosis to make 2 primary oocytes which then enters meiosis I but stop at prophase I. During puberty, 1 primary oocyte re-enters meiosis I once a month and this occurs within follicle cell which provides protection and nourishment. After meiosis I, cytokinesis occurs unequally to make a secondary oocyte that is big and contains most of the cytoplasm and organelles to provide sufficient materials for future zygote. One small daughter cell called polar body is also made with minimal resources. Secondary oocyte is dormant and does not enter meiosis II

Question 23

Ovulation

Answer 23

occurs when secondary oocyte is released from follicle and travels through oviduct where it can be fertilized by sperm. Once fertilized, ova begins meiosis II and cytokinesis is uneven to make a mature ovum with many recourses and polar body that will disintegrate

Question 24

Ovarian cycle

Answer 24

Follicular phase, ovulation, luteal phase

Question 25

Follicular phase

Answer 25

First step of ovarian cycle. Follicle develops and secretes estrogen, allowing primary oocyte to develop into secondary oocyte

Question 26

Ovulation

Answer 26

Second step of ovarian cycle. Mature ovum released from follicle which is now called corpus luteum

Question 27

Luteal phase

Answer 27

Third step of ovarian cycle. Corpus luteum secretes estrogen and progesterone

Question 28

Menstrual cycle

Answer 28

Proliferative phase, secretory phase and menstrual phase

Question 29

Proliferative phase

Answer 29

First step of menstrual cycle. Endometrium thickens in preparation of embryo

Question 30

Secretory phase

Answer 30

Second step of menstrual cycle. After ovulation, endometrium continues to be developed and maintained by corpus luteum

Question 31

Menstrual phase

Answer 31

Third step of menstrual cycle. In absence of hormones, endometrium is shed from uterus and excreted via vagina

Question 32

Ovarian cycle and menstrual cycle coordination by hypothalamic-pituitary-end-organ hormonal axis step 1/8

Answer 32

When estrogen and progesterone levels are low, hypothalamus secretes Gonadotropin Releasing Hormone (GnRH) to hypothalamic-pituitary portal blood system

Question 33

Ovarian cycle and menstrual cycle coordination by hypothalamic-pituitary-end-organ hormonal axis step 2/8

Answer 33

GnRH at anterior pituitary gland stimulates release of FSH and LH into circulation

Question 34

Ovarian cycle and menstrual cycle coordination by hypothalamic-pituitary-end-organ hormonal axis step 3/8

Answer 34

Follicular and proliferative phase: At ovaries, FSH stimulates follicle, resulting in development of follicle and enveloped oocyte. Estrogen is also secreted by follicle which causes endometrium to proliferate

Question 35

Ovarian cycle and menstrual cycle coordination by hypothalamic-pituitary-end-organ hormonal axis step 4/8

Answer 35

As estrogen levels rise, hypothalamus is stimulate to make more GnRH which causes anterior pituitary to release large amount of LH in surge

Question 36

Ovarian cycle and menstrual cycle coordination by hypothalamic-pituitary-end-organ hormonal axis step 5/8

Answer 36

Ovulation: LH surge triggers release of ovum from developing follicle, leaves the ovary with an empty follicle called corpus luteum and a naked secondary oocyte

Question 37

Ovarian cycle and menstrual cycle coordination by hypothalamic-pituitary-end-organ hormonal axis step 6/8

Answer 37

Luteal and secondary phase: Corpus luteum develops and secretes estrogen and progesterone to stimulate endometrium thickening with blood vessels and nutrients, preparing uterus for implantation

Question 38

Ovarian cycle and menstrual cycle coordination by hypothalamic-pituitary-end-organ hormonal axis step 7/8

Answer 38

Overtime, high levels of estrogen and progesterone reach the hypothalamus and anterior pituitary in negative feedback loop to stop production of GnRH, FSH and LH

Question 39

Ovarian cycle and menstrual cycle coordination by hypothalamic-pituitary-end-organ hormonal axis step 8/8

Answer 39

Lack of FSH and LH causes disintegration of corpus luteum, resulting in no progesterone and estrogen, endometrium growth stops and is sloughed off and excreted. In pregnancy, fertilized ovum is implanted before corpus luteum degrades and human chorionic gonadotropic (hCG) hormone is secreted to maintain corpus luteum in place of FSH and LH. Later, placenta makes progesterone in place of corpus luteum to maintain endometrium

Question 40

Ovum structure from innermost to outermost

Answer 40

Vitelline layer, peri-vitelline space, zona pellucida, corona radiata

Question 41

Vitelline layer

Answer 41

Innermost layer of ovum structure. Transparent, noncellular layer secreted by oocyte

Question 42

Peri-vitelline space

Answer 42

Third outermost layer of ovum structure. Space between vitelline layer and zone pellucida

Question 43

Zona pellucida

Answer 43

Second outermost layer of ovum structure. Extracellular matrix layer secreted by follicular cells and oocyte, composed of glycoproteins

Question 44

Corona radiata

Answer 44

Outermost layer of ovum structure. Thick outer layer composed of follicular cells

Question 45

Fertilization

Answer 45

Lifespan of secondary oocyte is 24 hours post ovulation, fertilization can occur in a 1 to 2 day period every menstrual cycle. Consists of capacitation, acrosome reaction, blocking polyspermy

Question 46

Capacitation

Answer 46

First part of fertilization. Thousands of sperm enter vagina and uterine secretions dissolve cholesterol coat on sperm to improve motility to a hyperactive state and destabilizes acrosome cap for acrosomal reaction upon contact with oocyte

Question 47

Acrosome reaction

Answer 47

Second part of fertilization. Sperm breaks through corona radiata of secondary oocyte. When one sperm reaches zona pellucida, the acrosome on anterior head of sperm is triggered to undergo an acrosomal reaction which causes sperm to release digestive enzymes within acrosome to soften glycoprotein matrix. This allows sperm to reach oocyte membrane and the 2 membranes fuse to make an acrosomal process, which is a bridge between 2 cytoplasms. This allows sperm to inject its nucleus and centriole into ooplasm and fertilize oocyte. This triggers secondary oocyte to complete meiosis II and become mature, fertilized ovum that travels through oviduct and to uterus to implant onto endometrium

Question 48

Blocking polyspermy

Answer 48

Third part of fertilization. Oocyte undergo 2 changes to prevent fertilization boy many sperms and prevent polyploidy (2 or more copies of each chromosome). Consists of fast block and slow block (cortical reaction)

Question 49

Fast block

Answer 49

Part of blocking polyspermy which is the third part of fertilization. Immediately after fertilization, oocyte depolarizes by allowing Na+ to diffuse into ooplasm which prevents fertilization by multiple sperms

Question 50

Slow block (cortical reaction)

Answer 50

Part of blocking polyspermy which is the third part of fertilization. Fusion of 2 membranes triggers release of Ca2+ into ooplasm, triggering release of cortical vesicles within the ooplasm which contain enzymes that destroy sperm binding sites, thicken glycoprotein matrix to harden the vitelline membrane and absorb water to swell and push vitelline membrane further from plasma membrane

Question 51

Multiple pregnancies

Answer 51

Monozygotic twins and dizygotic twins

Question 52

Monozygotic twins

Answer 52

Identical twins, one zygote splits to two. If division is at 2-cell stage, twins develop separate chorions and placentas. If division is at blastula stage, twins have a single chorionic sac and share a single placenta, and possibly share an amnion

Question 53

Dizygotic twins

Answer 53

Fraternal twins, female ovulates many oocytes that are fertilized by different sperms to make zygotes with their own placenta, amnion and chorion