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Learning Objectives for Reproduction Male Reproductive System 1. Male and female reproductive anatomy 2. Male and female gamete and sex hormone production • Testes (within the scrotum) produce sperm and regulation • Sperm are delivered to the exterior through a 3. Changes that occur in sperm and egg before and during system of ducts fertilization (chromosome number reduction) – Epididymis, ductus deferens, ejaculatory duct, and 4. Fetal Development the 5. Adaptations to maternal body during pregnancy 6. Guest lecturer –Dr. Jason Ross (Estrus cycle and Porcine Reproduction)

Overview of Reproductive System

Ureter Urinary bladder • Secondary sex characteristics Prostatic urethra Peritoneum – develop at puberty to attract a mate Seminal Membranous urethra • pubic, axillary and facial hair vesicle Ampulla of Urogenital • scent glands, body morphology and low‐pitched voice ductus diaphragm deferens in males Pubis Ejaculatory Corpus duct cavernosum Rectum Corpus Prostate spongiosum Bulbourethral Spongy urethra gland Epididymis Anus Glans penis Bulb of penis Prepuce Ductus (vas) Testis External deferens Scrotum urethral orifice

Figure 27.1

The Scrotum The Scrotum

• Sac of skin and superficial • Temperature is kept constant by two sets of – Hangs outside the abdominopelvic cavity muscles – Contains paired testes – Smooth muscle that wrinkles scrotal skin (dartos • 3C lower than core body temperature (temperature muscle) necessary for sperm production) – Bands of skeletal muscle that elevate the testes (cremaster muscles)

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Countercurrent Heat Exchanger

Urinary bladder Superficial inguinal ring (end of inguinal canal) Testicular artery Spermatic cord Ductus (vas) deferens Penis Autonomic Middle septum nerve fibers of scrotum Pampiniform Cremaster muscle venous plexus External spermatic Epididymis fascia Tunica vaginalis (from peritoneum) Superficial fascia Tunica albuginea containing Scrotum dartos of testis muscle Internal spermatic Skin fascia

Figure 27.2

The Testes Spermatic cord

Blood vessels • Blood supply and nerves –testicular arteries Ductus (vas) –testicular veins deferens Head of epididymis Testis •Spermatic cord encloses: Efferent ductule Seminiferous – nerve fibers tubule Rete testis Lobule – blood vessels Straight tubule Septum Tunica albuginea Body of epididymis – lymphatics Tunica vaginalis Duct of epididymis Cavity of Tail of epididymis tunica vaginalis (a)

Figure 27.3a

Seminal Vesicles Prostate viscous alkaline seminal fluid milky, slightly acid fluid Spermatic Ducts – Fructose, ascorbic acid, – Contains citrate and coagulating enzyme and enzymes • Epididymis (head, body and tail) prostaglandins – 70% of the volume of – Plays a role in the – 6 m long coiled duct semen activation of sperm – site of sperm maturation and storage (fertile for 60 days) Accessory Glands

• Ductus deferens (peristalsis during orgasm) Bulbourethral Glands – 45 cm long Prior to ejaculation ‐ thick, clear mucus – Lubricates the glans penis • Ejaculatory duct – Neutralizes traces of acidic urine in the urethra – 2 cm

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Semen Semen

• Mixture of sperm and accessory gland • Alkalinity neutralizes acid in the male urethra secretions and female • Contains nutrients • Antibiotic chemicals destroy certain bacteria • Protects and activates sperm • Only 2–5 ml of semen are ejaculated, • Facilitates sperm movement containing 20–150 million sperm/ml • Prostaglandins in semen – Decrease the viscosity of mucus in the – Stimulate reverse peristalsis in the

Sertoli cell function Lumen Mature Sperm • Nourish developing spermatozoa

Spermatogonium • Intracellular junctions form blood‐testes barrier

Sertoli cell • Produce inhibin – represses FSH • Secrete androgen‐binding protein (ABP)

Basal Lamina • Produce mullerian duct‐inhibiting substance surrounding seminiferous (MIS) tubule

Leydig cell

Leydig Cell Function Spermatozoon

• Secrete androgens – Testosterone – Dihydrotestosterone – Androstenedione – Dihydroepiandrosterone Sustentacular = sertoli Interstitial = leydig

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Figure 27.15

DNA turned off Meiosis events: 1. Introduce genetic variability 2. Reduction of chromosome number

Testicular hormones

• Leydig: FSH increases LH receptor number • Leydig: LH increases Testosterone (T) synthesis

• Sertoli: FSH stimulates production of androgen‐binding protein (ABP) • ABP binds T, thus increasing concentration in Testes • Increased T stimulates spermatogenesis

Figure 27.13 Testosterone Functions

• Differentiation of fetal male internal genitalia • Spermatogenesis • Development of secondary sexual characteristics • Libido • Muscle development, skeletal growth • Red blood cell production

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Female Reproductive System Secondary Sex Organs • Female Duct system • Produce and deliver gametes uterine tubes, uterus, vagina • Provide nutrition • and room for External genitalia fetal – , minora, and development – • Give birth accessory glands beneath skin provide • Nourish infant lubrication

Figure 28.2 Figure 28.3a

Uterine Tubes Uterus • Ampulla • Cervix: narrow neck, or outlet; projects into – Usual site of fertilization the vagina • Ciliated fibriae of infundibulum move oocyte • Fundus: rounded superior region into uterine tube • Isthmus: narrowed inferior region • Oocyte is carried along by peristalsis and ciliary action • Cervical glands secrete mucus • Nonciliated cells nourish the oocyte and the – block sperm entry except during midcycle sperm

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Vagina and Sexual Cycle

• Birth canal and organ of copulation • Sexual cycle ‐ events recurring every month when • Extends between the bladder and the rectum pregnancy does not occur from the cervix to the exterior – ovarian cycle = events in – • Urethra embedded in the anterior wall Menstrual/estrous cycle = parallel changes in uterus

• Reproductive cycle ‐ events occurring between fertilization and birth

Ovarian Cycle

• Monthly series of events associated with the

maturation of an egg Primary Vesicular Corpus follicle follicle luteum Degenerating Secondary Ovulation • Two consecutive phases follicle – Follicular phase: period of follicle growth – Ovulation occurs midcycle Follicular Ovulation phase – Luteal phase: period of corpus luteum activity

Figure 27.20b

Follicular Phase Follicular Phase

• Primordial follicle becomes primary follicle 3. Primary follicle becomes a secondary follicle 1. The primordial follicle is activated • Stratified epithelium (granulosa cells) forms around • Squamouslike cells become cuboidal oocyte 2. Follicle enlarges to become a primary (1) follicle • Granulosa cells and oocyte guide one another’s development 4. Secondary follicle becomes a late secondary follicle • Theca and granulosa cells cooperate to produce • forms around the oocyte • Fluid begins to accumulate

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Follicular Phase

5. Late secondary follicle becomes a vesicular follicle • Antrum forms and expands to isolate the oocyte with its corona radiata on a stalk • Vesicular follicle bulges from the external surface of the • The primary oocyte completes meiosis I

E2 synthesis: two‐cell model Figure 28.14

Hypothalamus Hypothalamus

5

GnRH 4 Positive feedback exerted 8 Travels via portal blood by large in 1 output. LH

Anterior pituitary 1 5 LH surge Estrogen Inhibin FSH FSH LH Ruptured 6 22 follicle 8

3 Slightly elevated 7 estrogen Thecal and rising cells (a) Fluctuation of gonadotropin levels: Fluctuating inhibin levels of pituitary gonadotropins (follicle‐stimulating levels. Granulosa Androgens Corpus luteum cells Mature follicle Ovulated hormone and luteinizing hormone) in the blood Convert secondary regulate the events of the ovarian cycle. Inhibin androgens to 2 oocyte estrogens Late follicular and Early and midfollicular phases luteal phases

Figure 27.19 Figure 27.20a

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Function/Targets of E2 Menstruation in mammals?

Main E2 target is reproductive tract • Loss of endometrial lining through blood flow 1. Vaginal mucous increased limited to primates 2. Increased blood flow • Other species resorb the lining 3. Genital swelling • /Estrous cycle 4. Growth of Uterus

Estrous v Estrus Ovulation

• Estrous = the cycle • Ovary wall ruptures and expels the secondary • Estrus –stage of the estrous cycle when oocyte with its corona radiata animals are in behavioral heat (high estrogen) • Mittelschmerz: twinge of pain sometimes felt at ovulation • Mono‐ or Poly‐ovulatory

Luteal Phase Luteal Phase

• Ruptured follicle collapses • If no pregnancy, the corpus luteum • Granulosa cells and internal thecal cells form degenerates into a corpus albicans corpus luteum • If pregnancy occurs, corpus luteum produces • Corpus luteum secretes progesterone and hormones until the placenta takes over estrogen

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Maternal Recognition of Pregnancy Cow: Interferon Tau Pig: Estrogen Horse: Conceptus/unknown protein

– secreted by blastocyte within 9 days of conception – prevents involution of corpus luteum – detected by pregnancy tests

Hormone Levels and Pregnancy Uterine (Menstrual/Estrous) Cycle

• Cyclic changes in in response to ovarian hormones • Three phases 1. Menstrual/resorbtion phase 2. Proliferative (preovulatory) phase 3. Secretory (postovulatory) phase (most constant in length)

Uterine Cycle

• Menstrual/resorbtive phase – Ovarian hormones are at their lowest levels – Gonadotropins are beginning to rise – Stratum functionalis is shed and the menstrual flow occurs

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Uterine Cycle Uterine Cycle

• Proliferative phase • Secretory phase – Estrogen levels prompt generation of new – Progesterone levels prompt functional layer and increased synthesis of • Further development of endometrium progesterone receptors in endometrium • Glandular secretion of glycogen – Glands enlarge and spiral arteries increase in • Formation of the cervical mucus plug number

Endometrial Blood vessels glands Uterine Cycle

Menstrual • If fertilization does not occur flow Functional layer – Corpus luteum degenerates Basal layer – Progesterone levels fall Days Menstrual Proliferative Secretory – Spiral arteries kink and spasm phase phase phase – Endometrial cells begin to die (d) The three phases of the uterine cycle: – Spiral arteries constrict again, then relax and open • Menstrual: Shedding of the functional layer of the endometrium. wide • Proliferative: Rebuilding of the functional layer of – Rush of blood fragments weakened capillary beds the endometrium. • Secretory: Begins immediately after ovulation. and the functional layer sloughs Enrichment of the blood supply and glandular secretion of nutrients prepare the endometrium to receive an embryo.

Figure 27.20d

Two Sexes Sexual reproduction • Male and female gametes (sex cells) combine their genes to form a fertilized egg (zygote) • each offspring has 2 parents and receives genetic material from both – one gamete has motility (sperm) • provides genetic diversity • parent producing sperm considered male • foundation for survival and evolution of species • has Y chromosome – other gamete (egg or ovum) contains nutrients for developing zygote • parent producing eggs considered female • in mammals female also provides shelter for developing fetus (uterus and placenta)

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Oocyte –2 meiotic divisions Meiotic division

#1 • Cell division without replication Begins in fetal development – primordial follicles • Chromosomal reduction Completed at time of ovulation – 46 diploid  23 haploid • Provides half genetic material from each parent #2 Occurs at fertilization

Very few follicles will complete both divisions

Pregnancy lengths

Species Gestation Human 266 Mouse/rat 21 Cat/dog 65‐70 Pig 114 Goat 145 Sheep 150 Cow 284 Elephant ~640

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Hormones of Pregnancy Hormones of Pregnancy • Progesterone • Estrogens – secreted by placenta and corpus luteum – increases to 30 times normal before birth – suppresses secretion of FSH and LH preventing – corpus luteum is source until placenta takes over follicular development – causes uterine, mammary duct and breast – prevents menstruation, thickens endometrium enlargement – stimulates development of acini in breast

Organ development in utero Role of Sex Chromosomes

1 2 3 4 5 6 7 8 9 10 11 12 20 28 38 Pre‐organogenesis Central nervous system • Our cells contain 23 pairs of chromosomes Heart – 22 pairs of autosomes Ear

Eye – 1 pair of sex chromosomes (XY males: XX females) U limb • males produce 50% Y carrying sperm and 50% X L limb carrying Lip • all eggs carry the X chromosome Teeth

Palate External Genitalia • Sex of child determined by type of sperm that fertilizes mother’s egg

Death Major malformations Functional defects and minor malformations

Wolffian ducts –male Wolffian ducts –male Mullerian ducts ‐ female Mullerian ducts ‐ female • Genetic male: • Absence of MIS – Testosterone and Mullerian inhibiting substance • Mullerian ducts proliferate forming uterus, • Testosterone uterine tubes, upper 2/3 of vagina – promotes development of Wolffian ducts • By week 8: full development into female • MIS genitalia – causes regression of mullerian ducts • Absence of androgens (T), wolffian ducts degenerate

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Mesonephros Mesonephric Testes Efferent ductules Gonadal ridge (Wolffian) duct Paramesonephric Metanephros (Müllerian) duct Epididymis (kidney) Mullerian Cloaca duct (degenerating) Wolffian duct forming the ductus deferens Urinary bladder 5- to 6-week embryo: sexually indifferent stage Seminal vesicle

Urogenital sinus Sex‐determining region Y ‐ SRY gene forming the urethra 7- to 8-week male embryo

Copyright © 2010 Pearson Education, Inc. Copyright © 2010 Pearson Education, Inc.

Ovaries Developmental problems Mullerian duct forming the • Every 4.5 minutes a baby with a birth defect is uterine tube Wolffian duct born (degenerating) • 15‐25% genetic reasons Fused Mullerian • 4% ‐ maternal condition ducts forming the uterus • 3% ‐ maternal infections Urinary bladder • 1‐2% ‐ deformations (u. cord) (moved aside) Urogenital sinus • 65% unknown etiology forming the urethra and lower vagina 8- to 9-week female fetus

Copyright © 2010 Pearson Education, Inc.

Male psuedohermaphrodite (XY) Female psuedohermaphrodite Androgen Insensitivity Syndrome (AIS) Have ovaries ‐ but male external genitalia Has testes (usually in body cavity) Female XX but female external genitalia (can be ambiguous) Congenital Adrenal Hyperplasia ‐ adrenal glands Testicular feminization in men is X‐linked overproduce testosterone Lack androgen receptor for male sexual development Body doesn’t respond to androgen being produced Cattle: Anastomosis – interconnection of blood vessels Male hormone pass into female in twin pregnancy Exchange of blood cells from male to female ‐ stimulates male duct development Infertile female ‐ Freemartin

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Hypothalamus Hypothalamus Anestrus – without cyclicity 5

GnRH 4 Positive feedback exerted 8 Travels via portal blood by large in • Pregnancy estrogen 1 output. • Lactation

Anterior pituitary • Presence of offspring 1 5 Progesterone LH surge Estrogen Inhibin • Season FSH LH Ruptured 6 22 follicle 8 • Stress 3 Slightly elevated 7 • Pathology estrogen Thecal and rising cells inhibin levels. Granulosa Androgens Corpus luteum • Nutritional Status cells Mature follicle Ovulated Convert secondary Inhibin androgens to 2 oocyte estrogens Late follicular and Early and midfollicular phases luteal phases

Figure 27.19

Gestational Anestrus Seasonal Anestrus • Progesterone (from CL/placenta) inhibits GnRH • Means to give birth when environment is favorable • Prevents FSH/LH secretion; no follicle • Pre‐attachment embryo survival low during high development temp’s (Heat stress) • Fall conception –moderate temp’s • Birth during spring – nutritional conditions better (e.g. for lactation) • This is controlled by photoperiod

Seasonal Anestrus ‐ Mare Seasonal Anestrus ‐ Sheep

• Cycles in spring • Cycles in fall • Conceives before summer • Short pregnancy (5 mo) • Long pregnancy (11 mo) • Lamb born in spring, optimum time for birth • Foal born in spring, optimum time for birth

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Lactational Anestrus

• Cyclicity completely suppressed in sow with milking • On weaning; sow displays estrus; ovulates within 4‐ 8d • Suckled cow; cyclicity delayed by 60d after birth • Suckling session <2 per day • >2 sucking sessions per day = postpartum anestrus • Thus, two suckling sessions per day is threshold

Fig. 7‐8

• Teat stimulation – inhibition of GnRH release from anterior lobe • Intense suckling –low blood LH • Weaning –increase in LH

Postpartum Anestrus Acyclicity in women

• Negative energy balance • Amenorrhea –absence of menses over long • Absence of GnRH pulses from hypothalamus period of time • Inadequate secretion of gonadotrophins • Atheletes, anorexic patients • Inactive ovaries • Lactational amenorrhea –ovarian inactivity in women • High prolactin, decrease in GnRH frequency and amplitude, decrease in LH/FSH • Effective contraceptive <6mo

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