MT 7 - Reproduction

Question 1

87 Male genitals

Answer 1

Internal male genitals:
•Testes: Prod. 50-500 mill. sperm/day throug adult life. Prod. sex hormones.
•Epididymis: Point of maturation of sperm
•Ductus deferens: Carry mature sperm from epididymis to urethra.
•Accessory seminal glands
oSeminal vesicles: 60% of seminal fluid
oProstate gland=30% of seminal fluid
External male genitals: Penis, prepuce, muscles for protrusion, erection and ejaculation

Question 2

87 hormone regulation in the male reproductive system

Answer 2

-Roles of male reproductive system:
•Spermatogenesis, storage of spermatozoa and ejaculation
•Development and maintenance of 2´degree sexual characteristics
*Endocrine control: androgens synt. in testes. Secretion under hypothalamo-pituitary control
-Hormones:
1.Testosterone: prod. by Leydig’s cells
•Secr. controlled by LH-RH and LH
•Inhib. LH release
•Released into blood&lymph. Freely diffuses across cell membr.
2.Sertoli Cells: spermiocytogenesis and spermiomorphogenesis
3.FSH (Follicle stimulating): interacts with sertoli cells
•Stim. ABP prod.&spermatogenesis
•FSH+LH+Testosterone=Complete spermogenesis
4.ABP (Androgen-Binding)
•Prod. by sertoli cells due to paracrine effect of testosterone
•Binds to testosterone and transports it to epididymis for maturation of spermatozoa.
•Converts testosterone to DHT and estrogen.
5.Inhibin
•Paracrine, autocrine and endocrine action: Incr. spermatogenesis
•Activates aromatase enzyme
6.MIF (Mullerian Inhibitory Factor)
•Paracrine, autocrine and endocrine action
•Development of male gender
•-ve feedback action on pituitary FSH
•+ve feedback action on LH prod.
7.LH (Leutenising hormone)
•Stim. endogenous testosterone prod. by Leydig’s cells
8.Acrosin (protease) and its inhibitor (acrosin-binding protein): enabling penetration of oocyte by spermatozoa

Question 3

87 Spermatogenesis

Answer 3

-The process in which an animal produces spermatozoa from spermatogonial stem cells by way of mitosis and meiosis.
•Only completed when FSH and testosterone reach layer of germ cells
•Most stages require continuous supply of androgens
•Total cycle(gonia->zoa)=60-70 days
1.Spermatocytogenesis: Primordial germ cell->haploid spermatid
2.Spermiomorphogenesis: Haploid spermatid->Spermatozoa
a.Golgi phase
b.Cap phase
c.Acrosomal phase
d.Maturational phase

Question 4

88. The role of accessory sexual glands in males

Answer 4

•The glands are: seminal vesicles, prostate, Cowper’s gland, ampulla of the ductus deferens
•Make up a considerable portion of the seminal plasma, which serves as a vehicle for spermatozoa.
-Seminal vesicle: consist of a mass of lobes, divided by septile CT, containing SM elements.
*Secretion contains fructose, citric acid, phosphates, ascorbic acid and various prostaglandins.
*Role: prim. energy supply and activation of spermatozoa.
-Prostate: lobular gland located behind seminal vesicles
*Its serous secretion contains glycoproteids, phosphates, gluconidase, zinc, various cations and chloride.
*Role: induction of sperm-mobility
-Cowper’s gland – Bulbourethralis: lobular tuboloalveolar bodies, dissected by septile SM walls.
*Secretions: serous acidic liquid, leaves body during erection
*Role: damages sperm cells, decr. their motility, and enhances their agglutination.
-Ampulla: formed by a mass of tuboloalveolar glands embedded in deferent ducts
*Bull: secrets fructose and citric acid. Stallion: these substances lack, but there is a high conc. of ergothionine and a smaller amount of inositol
*Role: Not entirely defined, but most probably it facilitates passage of sperm.

Question 5

88 Male sexual reflexes

Answer 5

1. Erection:
   * Preparation->swelling of erectile tissue of penis via pudendal a. and protruding of penis from prepuce
   * Spraying: Urethra rinsed by secretion of Cowper’s gland
   * Then a rapid sequence, jumping and embracing reflexes
2. Intromission: Introduction and intromission of penis into vagina
   * Tissue of the erigated penis compresses the veins -> venal return of blood from erectile tissue during resting circumstances
3. Ejaculation:
   * After-push reflex: afferentation of ejaculatory reflex from mechanical stim. after immission of penis
   * Copulatory movements: afferent nerves projecting to lumbar centre of spinal cord; elicits ejaculation
   * Efferent branches of the reflex also acts: hypogastric plexus and motor impulse from int. pudendal n.

Question 6

89. phases of the estrus cycle

Answer 6

-Processes of female reproductive system are cyclic. The unit of these cycles is called estrus cycle
-The stages bw. consecutive periods of sexual sensitivity (the time between two ovulations)
-Sp. w. continous/periodical(seasonal)/where ovulation is induced by coitus or copulation(reflex ovulation)
-Seasonal estrus: After the onset of puberty, regular cycles occur only in certain seasons
-Seasonal monoestrus: in each sexually active season only one estrus cycle occurs
-Seasonal polyestrus: several estrus cycles occur
-Continuous estrus: From beginning of puberty, 21-days estrus cycles continuously occur
•Stages: Proestrus, Estrus, Metestrus, and Diestrus.
*Lack of estrus cycle: anestrus
•3 phases according to functioning of follicle:
1) Follicular phase: Preparation and maturation of the follicle. Days.
2) Ovulatory phase: Release of egg from ovaries. Fast-minutes.
3) Luteal phase: preparatory period for a possible fertilization in ovary
•Form. of corpus luteum from tissue residue remaining after ovulation
•Lining gets thicker.
•Ends in pregnancy or luteolysis

Question 7

89. phases of the estrus cycle: proestrus

Answer 7

•Significantly incr. plasma levels of E2 and drastic decr. P4 levels
•Morphology of genitalia:
*Fluid secr. by endometrium, “flowing” occurs. Bitch bleeds through vagina
•Behavioral changes:
*cow: mating movements with another cow
*bitch: vaginal fluid, containing pheromones, can excite the male

Question 8

89. phases of the estrus cycle: estrus

Answer 8

•Ovulation occurs (except for cow)
•Female “seeks” and “receives” male
•E2 peak, low P4 levels, LH peak
•Morphological changes:
*Vulva: swollen and edematous
*Cervix: opened, so spermatozoa can enter uterus
*Mucosa: swelling. Decr. inflam. cells, and incr. cornified cells on mucosa of bitch
*Decreased secr. and nr of erythrocytes
*Myometrium: In mare, muscular layer is relaxed. In cow, muscular layer contracts
•Behavioral changes: sexual sensitivity
*High E2 induce typical estral behavior to attract male and eliciting copulation
*Female turns her back to male, reveals vulva, urinates more often, and stops moving when pressed at her lumbar back
•Sow: back-pressure test. Same effect is elicited when she detects presence of pheromones in saliva of boar
•Cow: moves more than usually. Climbs up on her mates
•Mare: stallion guided to the mare->swings her tail and “flashes”.=jumping

Question 9

89. phases of the estrus cycle: Metestrus

Answer 9

• Decr. E2 and LH levels, still low P4 level.
• Average duration of metestrus is 2 days.
• Strong regression of morphological changes characterizing estrus can be observed.
• Estrual behavior stops

Question 10

89. phases of the estrus cycle: Diestrus

Answer 10

• Longest of all stages.
• Under the influence of P4: female does not pay any attention to male, or replies aggressively to its presence.
• Despite rising of E2 levels, estrual behavior is not experienced. Can be explained by the blocking effect of progesterone on CNS
• Due to the effect of progesterone, swelling of vulva stops, cervix closes, mucosa of vagina becomes dry and pale, and endometrium becomes even thinner and begins its secretory phase. In cow the myometrium is relaxed, while it is contracted in mare

Question 11

90. Cyclic function of the female reproductive organs: The cycle of the uterine tube

Answer 11

-Proestrus: 
•The tube gets rigid due to E2 perfusion
•Slow movements towards uterus, which promotes the reception of egg into the ampulla
•Enlargement of tube
Estrus/Ovulation:
•Cilia of mucosa help transporting the ovum.
•The tube also feeds the ovum/zygote
-Metestrus: effect of P4 dominate
•Stop of incr. blood flow to uterine tube
•Transport of ovum is accelerated
•Isthmus is opened
•Ovum passes towards direction of uterus

Question 12

90. Cyclic function of the female reproductive organs: The cycle of the uterus

Answer 12

-Proestrus and estrus:
•Proliferative phase, due to E4
•Incr. blood supply to uterine
•Mucosa becomes edematous
•Proliferation of glands begin
•Elevated metabolic rates in cells
-Metestrus:
•Secretory phase. Progesterone dominate.
•Mucosa becomes thick
•Glands of endothelium are further maturated and achieve their max. secretory capacity
•Decr. estrous hyperemia and motility of uterine muscles->advantageous environment for settling down of egg
-Diestrus:
•Without fertilization; involution phase
•Superficial layer of endometrium die and elements of the tissue dissociate and undergo resorption
-Anestrus:
•Resting stage
•Endometrium only consists of single layer
•Lumen is narrow
•Both uterine tubes and mucosa becomes thin

Question 13

90. Cyclic function of the female reproductive organs: The cycle of cervix

Answer 13

-Proestrus and estrus:
•Evolutional stage, i.e. the follicular phase.
•Tonicity of cervical muscles becomes enhanced, cervical ducts forms a “gate” to facilitate spermatozoa transport, and secr. of epithelial mucus enhances.
-Anestrus (or in case of fertilization):
•Stage of involution: prod. and consistency of cervical mucus decr.
•If fertilization does not take place by the end of the flourishing luteal phase of ovary, involution phase of cervix is terminated and being adjusted to a new cycle of the ovary: a new evolution phase begins

Question 14

90. Cyclic function of the female reproductive organs: The cycle of the vagina

Answer 14

-Proestrus and estrus:
•Incr. blood supply and thickness
•Enhance of vaginal mucosa secretion
->promotes copulation and fertilization
•Ratio of keratinized cells incr. at end of proestrus
•Ratio reaches its max. under estrus, providing a protection from effect of penis during copulation
-Metestrus and diestrus:
•Progesterone dominates
•Hyperemia and swelling of epithelium decr.
•Secr. gradually stops

Question 15

91. Hormonal changes during the estrus cycle: hormones and regulation

Answer 15

-Hormones: GnRH, Estrogen, Progesterone, PGF2, Oxytosin, LH and FSH
-Regulation:
•Via hypothalamus-pituitary axis.
*Controls GnRH cells via direct innervation, and ensuring base-level GnRH secr.
*Hypothalamic centres reg. by blood estrogen and progesterone levels->-ve feedback
-Estrogen:
*Levels dependent on follicular activity.
•Plasma estrogen are very low after ovulation as new follicles begin to mature (luteinisation stage).
•Inhibitory effect of P4 on CNS->no estrous behaviour shown

Question 16

91. Hormonal changes during the estrus cycle

Answer 16

1.Follicular phase: P4 decline, high E2+Low P4->estrous behaviour
2.Ovulation: rising E2 and low P4
3.Luteal phase:
a) PRL and incr. plasma P4 (because of ovulation and luteinization) -> no estrous behaviour
b) Luteolysis: occur at end of luteal phase when no pregnancy happens
*incr. PGF2 alpha and oxytosin, decr. P4 (degr. of corpus luteum to corpus albicans)
-Final maturation:
*Mare – requires continuously elevated FSH & LH levels
•Incr. E2 synt. Incr. FSH & LH stim.

Question 17

92. Hormonal effects in the ovary, hormones of the ovary

Answer 17

• Hormones: Estrogen, Progesterone, PRL, FSH, LH
• Estrogen:
  1. Follicular phase: incr. E2
  2. Ovulation: decr. E2, incr. PRL
  3. Luteal phase:
  a) PRL and incr. P4
  b) Luteolysis: decr. P4 rapidly
• Estrogen:
  1) Estrogen levels depend on follicular activity. Plasma estrogens are very low; therefore female is very sensitive to this hormone.
  2) All the follicles become atretic parallel to the decr. levels of estrogen.
  3) Follicular phase begins: A new group of follicles start to develop. Among these, only one can reach the stage of follicular rupture, while levels of progesterone start to decr. (luteolysis). High E2 level and lack of P4 inhibitory effects elicit estrus behavior.
  4) Levels of estrogen begin to decr., parallel to the elevation of PRL levels and ovulation.
• Progesterone:
  1) Luteal phase: initiated by PRL and incr. plasma P4 levels
• Ovulation and the following luteinization are responsible for most of the incr. plasma P4 levels
  2) Luteolysis: Uterine secr. of PGF2 alpha results in atrophy of corpus luteum. Plasma P4 levels decr. rapidly
• FSH: necessary for estrogen synt. and maturation of follicle.
• In most sp. but mare, nr. of FSH receptors incr. in granulosa cells of follicle during follicular phase-> estrogen prod. and maturation of follicle will enhance-> dominant follicle
• LH: essential for synt. of progesterone and estrogen
• In the inital phase of follicular maturation, all receptors are located on theca cells. Later, receptors also appear on granulosa cells.
• Receptors necessary for transformation of granulosa cells into granulosa-lutein cells, and later for form. of corpus luteum cells

Question 18

93. Fertilization

Answer 18

1.Spermatozoa ascend to cervix, is transp. to oviduct and undergo capacitation (maturation)
2.Ovulated egg goes to ampulla in fallopian tube
3.Sperm bind oocyte
4.Acrosome reaction: acrosin penetrate zona pellucida and fuse with plasma membrane
5.Cortical reaction: cortical granules released from oocyte, digest zona pellucida-sperm receptors elim.
=block to polyspermy
6.Genetic transfer: nucleus of spermatozoon enters oocyte cytoplasm and de-condenses->form. of male pronucleus
-Hormones:
•Hyaluronidase/CPE(corona penetrating enzyme): dissolves corona radiata
•Acrosin: penetration of zona pellucida
•Cortical granules: digest zona pellucida
•Oxytosin: elicitated by copulation reflex-incr. motility of uterus
-Post-fertilisation:
1.Fusion of sperm and oocyte
2.Nuclear envelope of sperm disappears
3.Chromatin loosens
4.Chromatin of sperm and egg are encapsulated by common nuclear membrane

Question 19

93. Endocrinology of pregnancy

Answer 19

-Steps:
1.Embryo develops into a blastocyst
2.Hatching of blastocyst from the zona
3.Implantation and nidation
4.Form. of extra-embryonic membranes
5.Maternal recognition of pregnancy
-Hormones:
•Maintained by P4: inhib. luteolysis
*Bitch: P4 levels maintain high throughout pregnancy
*Other sp: Corpus luteum is transformed to CL graviditatis -which prod. P4
*Early embryo secr. interferon tau in big amounts
*Inhib. PGF synt.->no luteolysis. Corpus luteum continues to maintain P4 levels.
•Ovary is only initial source. Later:
*Sp. indep. of CL (Primates, Eq, sheep and cow): placenta transforms into endocrine organ and prod. P4
*Sp. dep. of CL (Ca, Su, Goat): CL prod. P4 throughout pregnancy
-1st trimester: LH incr., P4 incr.
-P4 role: ensures safety of implanted embryo, prepares mam. gl. for lactation, and develops cervical and vaginal involution.
-Estrogen/oxytocin: prod. by myometrium. Inhib. new fertilization.
-Relaxin: Prod. by ovary/placenta. Relaxes birth canal for parturition

Question 20

94. Fetoplacental endocrine unit

Answer 20

•Fetoplacental (fetomaternal) unit: means that hormone production and steroid genesis in the fetal adrenal cortex are interdependent.
*P4 secr by placenta, reaches adrenal cortex through fetal circulation, and acts as a precursor for synt of cortisol.
*DHEA and 16-hydroxide-HEA are formed in fetal adrenal gland from pregnenolone, synt in fetal liver.
*These compounds reach the placenta in conjugated forms, then to E2 which then enter the maternal circulation. So both the placenta and the fetus mutually utilize precursors synthetized in any of them.
•Placental hormones:
*Progesterone: in CL-independent species; primates, horse, sheep, cow
*Choriogonadotropins: hCG, eCG
*Placental lactogens (PL)
*Estrogen: fetur-mother interaction
*Chorionic somatomammotropin (CS)
•P4 is secr by placenta and reaches adrenal cortex via fetal circulation. Acts as precursor for synt of cortisol
•PL has PRL-like and somatotropic effects; produced from mid-gestation until the end of it
•CS stimulates growth and lactation. Unable to pass into fetus, so it is a maternal growth hormone
•Human chorionic gonadotropin (hCG): prod in human placenta
*Role in human: recognition and maintanence of pregnancy. Corpus luteum stimulation (P4 production).
*Role in animals: Pharmacological use – LH-like effects
•Equine chorionic gonadotropin (eCG): prod in chorion of pregnant mares
*Role in mare: prod of accessory CL during pregnancy
*Role in other animals: pharmacological use – FSH-like effect
•Fetus mother interaction: Essential for E2 synt. Fetus has no enzymes necessary for pregnenolone synthesis. Placenta has no enzymes necessary for transformation of pregnenolone. Therefore, pregnenolone is transported to fetal side for synthesis.

Question 21

95. Endocrinology of parturition; birth

Answer 21

• Phase 1 – preparation dilation:
  a) Preparatory phase:
• Endamatous infiltration and swelling of soft birth canals.
• Rump and abd. lowered due to relaxation of pelvic lig.
• Indicated by retiring behaviour of female, and 0,5-1,0 degree decr. of body temp.
• Uterus reaches a tonic status. No labour-pains.
  b) Phase of opening:
• Further dilation of birth canals
• Rythmic contractions in uterus->labor-pains
• Connection bw fetal and maternal parts of placenta becomes looser. Fetal membranes goes to vaginal slot->final dilation of birth canals
• Preparatory pains begin
• Phase 2 – contraction (expulsion)
  a) Uterine contractions incr. by oxytocin and abd. pressure, help the expulsion of foetus
  b) Head is pushed out
• Most intensive stage, with most severe pain.
• Followed by a short pause and gathering of strength
  c) Delivery usually in lying position. Duration is variable
• Phase 3 – elimination of membranes:
  a) After stop of uterine contractions, short resting stage, then after-pain starts-serves for the final expelling of the fetal membranes=afterbirth
  b) After finishing parturition, morphological recovery of uterus begins-to reach pre-gravid status
• Ovary is reactivated, new cycle starts, and uterus becomes suitable for new pregnancy

Question 22

96. Mammary gland development

Answer 22

-Mammals: milk only natural way to feed newborn
-Gives nutrient and fluid until newborn is able to feed alone + significant role in protection against pathogenes
-Mammogenesis->Lactogenesis->Galactogenesis->Ejection->Involution
-Mammogenesis: development of the gland
-Lactogenesis: milk synt. and milk secr..
-Galactopoesis: maintenance of milk prod.
-Ejection: milk let down.
-Involution: regressive transform. of gland
-Mammogenesis:
*During embryonic life.
*Special sensitizing phase
*Inhib. by androgens in male embryo. Limited growth during prepubertal period.
•Puberty: dev. of mam. ducts happens due to E2, P4, GH. and GC stim.
•Lactation: further alveolar/lobular growth happens until peak lactation, then regression happens. Mam. epithelial cells start to secr.
•Dry period: secretory cells undergo regression, preparation for next lactation phase
•Dev. of alveoli: E2, GH, corticosteroids
•Dev. of duct system: PRL and P4

Question 23

96. Mammary gland development, lactogenesis: Lactogenesis

Answer 23

•Series of cellular changes where mam. epithelial cells are converted from nonsecretory state to secretory state
•Normally associated with end of pregnancy and around time of parturition
•Two-stage process:
1.From middle of pregnancy, mam. gl. prepares for milk prod. IC tight junctions are dev. Milk prod. is inhib. by P4 or E2. Precolostrum is prod.
2.After delivery release from P4/E2 inhib.: PRL incr. Colostrum and milk are prod..

Question 24

96. Mammary gland development, lactogenesis: Galactopoesis

Answer 24

•=Maintenance of lactation once it has been established
•Reg. by galactopoietic hormones and local mam. factors
•Milk removal also influences galactopoesis.
-Without frequent emptying of the mam. gl, milk synt. will not persist in spite of hormones.
-Conversely, maintenance of intense suckling or milking stim. will not maintain lactation indefinitely. Nevertheless, suckling or actual removal of milk is required to maintain lactation.

Question 25

97. Reproduction of birds: Male bird

Answer 25

-2 testes but no seminal vesicles or prostate gl
-Testes remain within abd. cavity througout bird’s life
-*consists of many convoluted ducts that prod. spermatozoa
*lead to ductus deferens: coveys sperm to papilla in cloaca
•The two papilla form phallus/copulatory organ located in wall of cloaca
•No acc. glands->semen more dense
•Spermiocytogenesis and spermiomorphogenesis during puberty happens in seminiferous tubules, with contribution of Sertoli cells. Function reg. by FSH.
•Spermiums spend only short time in epidydimis; then 90% accumulate and reside in ductus deferens
•Ductus deferens contraction stim. ejaculation
Hormones:
•Leydig cells synt. androgens. LH receptors on the surface=reg. is LH related.
•Testis prod. P4 and E2 as well
•Sertoli cells also prod. androgens
•Hypothalamus: Gn-RH secretion is influenced by the season, amount of daily light and neg. feed-back effect of testosteron.
•Testosteron converted to 5 ß-DHT-t in CNS (inactive)
•Adenohypophysis: prod. LH, and FSH
•Androgens: role in forming sexual dimorphism, and help epididymis, ductus defferentis, and copulatory organs to develope

Question 26

97. Reproduction of birds: Female bird

Answer 26

-Three-staged Development:
1. At the beginning of prepuberty (1-12 weeks) small white follicles
2. Intermediate-phase just before sexual maturation: small-, med- and large-follicles.
3. At maturation: small, med and large yellow follicles
•7-10 days before ovulation big yellow follicles are connected to the ovary by manubrium. The largest preovulatory follicle ruptures along stigma and ovum gets into infundibulum.
•Follicular growth is stim. by FSH, ovulation is stim. by LH
Hormones:
-Estrogens: Estron (E1) and (E2) take part in reprod.
•Role: morphofunctional preparation of oviduct and of Ca-metabolism for egg prod.
•Incr. deposition of abd. fat->creation of sec. sexual characteristics and adequate behavior in successive reprod. periods.
•Ovary also prod. androgens
-Progesterone
•Plasma P4 level incr. in second phase of follicle maturation (age 13-15 weeks) together with incr. of LH.
Just before maturation LH- and P4 level decr.
•In sexually matured birds, plasma P4 is low and fluctuates. 4-7 hours before ovulation it prod. a preovulatory peak->ovulation.
-LH - FSH
•Preovulatory peaks take place, process is biphased:
1. Sensitizing phase: hypothalamic P4 receptors are incr. by high E and P4, so high P4 stim. the GnRH-prod.
2. Inductive phase: constant rise of preovulatory P4 peak is enough to stim. LH secr. by sensitized hypothalamo-hypophyseal axis.

Question 27

97. Reproduction of birds: Brooding patch

Answer 27

•At the beginning of brooding the brood patch develops due to PRL influence in synergism with estrogens.
-Abd. skin becomes bare, epidermis thickens, underlying CT swells and abundant venous network proliferates in it. On this skin area heat transmission needed for hatching is extremely efficient.
•Thyroid hormones incr. basal metabolism, stim. PRL secr. and inhibit the function of gonades.

Question 28

97. Reproduction of birds: Formation of Egg

Answer 28

1.Infundibulum (25-30 min) 
o Engulf the preovulatory follicle 
o Spermium storing glands, fertilization
2.Magnum: (3 hours) 
o Longest part of oviduct
o Prod. albumen
o Egg-shell prod. begins when yolk reaches isthmus.
3.Isthmus: (1-2 hours) 
o Forms two fibrous cell membranes
o Organic granules are deposited on external surface of soft shell membr. (mamillary core)
4.Uterus: (19-20 hours) 
o From mamillary core mamill. knobs will dev., form. of calcification begins. 
o Albumen layers develop (plumping). Soft shell-membr. will stretch 
o Plumping is followed by shell form.
5.Uterovaginal sphincter (1 min)
o Transp. of egg to outside