Reproduction Flashcards
What is a teratoma?
Tumour formed by ectopic primordial germ cells. They’re usually benign, cystic tumours
What are germ cells?
Progenitors of sperm and egg. Arise outside gonads.
What are gonadal cords? What do they become and what is their significance?
Distal parts of many mesonephroc tubules fuse with invaginated coeliomic epithelial cords. They become infiltrated with primary germ cells and cavitation to form seminiferous ubules where spermatogenesis occurs.
What do the mesonephric tubules become?
Efferent ducts and rete testes which transport sperm to epididymis
What are Sertoli cells? Where are they derived from, what do they secrete and what is their function?
They are the first testis-unique cells to differentiate. They’re derived from coelomic epithelium and are critical for spermatogenesis. Secrete AMH in the embryo. Secrete inhibin and androgen binding protein later also
What is the role of AMH?
Initiates degeneration of progenitors of female reproductive ducts.
What are Leydig cells?
Cells of the testes that synthesise and secrete testosterone
What is the SRY gene? Briefly describe conditions such as XXY and XO.
= transcriptional regulatory gene that is activated within the progenitors of Sertoli cells.
XXY individuals are phenotypically male
XO individuals are phenotypically female
In females, what do the mesonephric tubules become?
Nothing. They degenerate.
What does Wnt4 do?
It has a suppressive effect on the differentiation of steroid-
producing cells. Important in ensuring females aren’t masculinised.
Overexpression in males may lead to cryptorchidism
In males, what does the mesonephric duct become?
The epididymis and the ductus deferens
What do the paramesonephric ducts become?
The uterine horns
How does the vagina form?
Evagination of the urogenital sinus plus the distal part of the paramesonephric duct
In females, the urethral folds and genital swellings form the…?
Labia
Scrotum in males
What does the gubernaculum form?
The scrotal ligament.
What is Klinefelter’s syndrome?
XXY genotype. Results from meiotic x-chromosome nondisjunction during oogenesis. Individuals are phenotypically male. Tortoiseshell cats.
What is a male pseudohermaphrodite? What about a female pseudohermaphrodite?
Male: phenotypically female with testes. Genotypically female (xx) but possess an autosomal gene with Y effect on their chromosomes. (Occurs in goats that are homozygous for polledness)
Female: phenotypically male with ovaries and testicular tissue present. Have an XX genotype with an SRY translocation
What is a freemartin?
Situation on cows with twins where blood crosses from one twin to the other. The XY present in the heifer calf prevents the development of paramesonephric ducts in the female . External genitalia often show some masculinisation
What are some basic differences between an oestrous cycle and menstrual cycle?
Species (non-primates vs primates) Length (28d vs 21d) Shedding of mucosa Sexual receptivity (heat) Length of follicular and lateral phases Time point of ovulation (oestrous cycle starts and ends with ovulation)
What are some things which may cause anouestrus?
Season Lactation Offspring Stress Pathology Pregnancy
What is the cycle length in sheep?
200-260 d (merino)
100-140d in blackface breeds
How is melatonin important in cycling?
Increased light -> decreased melatonin levels -> increased RF-aside related peptide-3 -> increased kisspeptin (in long day breeders) -> increased GnRH release
Pigs and ruminants have 21d oestrus cycles. Duration of oestrus differs how?
🐄 Cattle: 18hrs (ovulation is 10-11 hrs after end of oestrus) 🐑 Sheep: 24-36hrs (24-30 hours after beginning of oestrus) 🐐 Goats: 32-40hrs (30-36 hrs after beginning of oestrus) 🐖 Pigs: 2-3d (35-45hrs after beginning of oestrus) 🐎 Horses: 4-8d (1-2d before the end of oestrus)
Describe the oestrous cycle of the dog.
Oestrus occurs approximately every 7 months.
The beginning is marked by an LH surge which lasts 24-28hrs. Ovulation occurs approximately 2 days after the LH peak
Proestrus (when bleeding occurs) 9d on avg
Oestrus 8-9d
Dioestrus 57d in pregnant bitch
No sharp drop in progesterone
Canine oocytes are ovulated as primary oocytes. True or false?
True. Takes 48-72 hours to mature before fertilisation can occur
Which species are induced ovulates? What does this mean?
Cats and camelids.
The act of penetration stimulates ovulation
Briefly describe the oestrus cycle of cats.
Proestrus- 1.2 days
Oestrus- 7.2 days
Postoestrus- 8-10 days (if ovulation doesn’t occur)
Dioestrus- 40d in pseudopregnant, 60 days in pregnant queen
What are some signs to look out for of oestrus in cattle?
Proestrus/early oestrus: cows mounting, restlessness, vocalisation
Oestrus: standing to be mounted, ruffled tail hair, rubbed off tail paint
When and how often should a mare be teased? Why?
Daily from 3 days post partum until day 60 of pregnancy.
Necessary to detect when a mare is in oestrus
How might you detect oestrus in a dog?
Breeding reflexes
Vaginal exam (using speculum)
Exfoliative cytology
Serum progesterone levels
How might you manipulate the oestrous cycle?
Induce luteolysis (PGF2-alpha) Prolong the luteal phase (progesterone)
What are some reasons for wanting to synchronise oestrus?
- Improved oestrus detection rate
- Allows timed mating and AI
- More efficient use of AI
- Embryo transfer
PGF2-alpha only works on what sort of CLs?
CLs older than 5 days
What is hcG?
Human chorionic gonadotropins
LH-like function. If given to mare at right time (35mm follicle) high likelihood of her ovulating 36-42 hours later
What is the “ram effect”? In which breeds is it most pronounced?
Sudden introduction of rams to ewes that have been isolated from rams will induce ewes to start cycling. Most ewes will come into heat 17 or 25 days after the first ram (or teaser) introduction.
British breeds
What are the three major steps of AI?
- Collection of semen from the male
- Preservation and extension of sperm
- Insemination of the female
What is semen extender? What is it made of? What are it’s uses?
Protector of sperm! Protects sperm against possible damage by toxic seminal plasma. Basic components are:
1. Buffer (tris, citrate)
2. Sugar
3. Antibiotics
Used to enable ejavulate to split into several doses, to increase longevity of sperm outside tract, and allows shipping of semen.
Identify the site of natural semen deposition and AI in the various animals below: Cattle Horse Sheep Pig Dog
Cattle- vagina (uterus)
Horse- uterus (uterus)
Sheep- vagina (cervix if fresh, uterus if frozen)
Pig- uterus (uterus)
Dog- vagina (vagina if fresh, uterus if frozen)
If using frozen semen, when should you try to inseminate a mare for best chances of pregnancy?
Within 12 hours before ovulation or 6 hours after ovulation
What is ICSI?
Eggs are collected and 1 sperm is infected straight into egg
What is the mechanism of erection in a musculocavernous penis?
Increased blood flow + decreased venous return ➡️ engorgement of erectile tissue
(Stimulation leads to relaxation of the wall of coiled and deep arteries of the penis. There is also additional blood pumped in by contraction of the ischiocavernosus and bulbospongiosus)
What causes male and female dogs to be tied together?
Bulbous glandis enlargement (contractions of the muscles at the base of the penis prevents venous outflow). Also sphincter muscle of the vulva constricts and compresses the dorsal vein of the penis
What are some functions of the epididymis?
- Spermatozoal maturation
- acquisition of motility
- structural changes
- physiological changes - Water absorption
- Spermatazoal transport
- Blood-epididymis barrier
When do sperm gain motility?
Distal corpus (cavernosum?)
If the marked uterine inflammatory reaction that occurs with sperm entry does not resolve within 48 hours, what is the female at risk of?
Post-mating induced endometriosis
What are so,e barriers the sperm has to get through to reach the egg?
- Retrograde flow of sulfomucin and sialomucin
2. Phagocytosis (many neutrophils under the mucosa of the vagina and uterus)
What is the privileged pathway for sperm?
Pathway through the crypts of the cervix where sialomucin is produced (less viscous than sulfomucins produced in the apical portions)
What is decapacitation of sperm?
Removal of seminal plasma molecules and part of the plasma membrane on the head of sperm to allow binding to zone pellucida
What is the acrosomal reaction?
Process by which the membrane overlying the acrosomal me,brand fuses with the outer acrosomal membrane leading to vesiculation and pore formation
What is the cortical block?
Release of cortical granules into the perivitelline space which brings about a biochemical change in the zona pellucida that makes it impenetrable to other sperm
What is syngamy?
When the male pronucleus fuses with the female pronucleus
Once the sperm nears the oocyte, what series of steps occurs before embryogenesis can take place? (9)
Hyperactive motility (zigzagging) ➡️ binding to ZP ➡️ penetration of ZP ➡️ sperm-oocyte membrane fusion ➡️ sperm engulfment ➡️ decondensation of sperm nucleus ➡️ cortical block ➡️ formation of male pronucleus ➡️ syngamy
Where do the prostate and bulbourethral glands develop from?
The urogenital sinus
What innervates the gubernaculum?
The genitofemoral nerve
When is GnRH secretion increased in a ram?
Autumn (short day breeders)
Where is the “pulse generator” located in the brain?
Mediobasal hypothalamus
What stimulates the production and release of testosterone from Leydig cells?
LH (testosterone released is proportional to the amount of LH released)
What does FSH do in males?
Important to the developing testes before puberty. Stimulates production of androgen binding protein by Sertoli cells so that the steroid hormone accumulates at its site of action
What is inhibin?
Glycoprotein hormone produced by Sertoli cells in response to FSH. It has a negative feedback action on the hypothalamic-pituitary system to suppress the secretion of FSH
In males, where are oestrogens secreted from?
The Leydig or Sertoli cells
Spermatazoa are present in most rams by the time bodyweight reaches…?
28kg
What does maturation of the sperm in the epididymis involve?
Migration of the cytoplasmic dorplet from the proximal position near the head to the distal position of the end of the midpiece
In the ram and bull it takes approximately ____ days for the production of spermatazoa froma spermatagonium. The sperm appear in the ejaculate _____ days later.
50
10-14
What is unique about the female reproductive tract in birds?
They have a single ovary (usually the left one) that appears like a bunch of grapes
What are the main events characterising oestrus?
Follicles grow to maturity and rupture
Cervix opens
Vagina/vulva prepares fpr copulation
Why are the uterine horns convoluted in ruminants and pigs?
They’ve undergone caudal migration during embyogenesis
What are corpora lutea?
Spherical bodies consisting of endocrine cells which produce progesterone to support pregnancy. They develop from ruptured follicles. Form corpora albicantes if no pregnancy occurs.
What is the opening of the uterine infundibulum called?
Abdominal ostium
How does the cervix remain impenetrable from the external environment?
Cervical canal has interdigitating prominences or folds except at oestrus and parturition
Mucus plug
Briefly describe the 4 events that occur before implantation of the embryo.
- Dvpt within the zona pellucida (ootid to zygote to 2-cell embryo to morula to blastocyst)
- Hatching of the blastocyst
- Formation of extraembryonic membranes
- Maternal recognition of pregnancy
What does totipotent mean?
The ability of a single cell to give rise to a complete fully formed individual. The cells up to an 8-cell embryo are totipotent
How is the blastocoele formed in the blastocyst?
(Inner cells develop gap junctions which facilitate cell-cell communication, and the outer cells develop tight junctions which facilitate cell-cell adhesion)
A sodium pump is responsible for an increase in sodium and consequently water inside the embryo
How does hatching of the blastocyst occur?
Cells continue undergoing mitosis and fluid in blastocoele keeps increasing-> increasing pressure within zona pellucida.
Outer trophoblast cells also produce proteolytic enzymes which weaken the ZP.
Blastocyst contracts and relaxes -> pressure pulses -> rupture of ZP