Reproduction Flashcards
(101 cards)
1
Q
What are the 2 types of castration?
A
Open castration - vaginal tunic is opened
Closed castration - vaginal tunic is not opened
2
Q
Define cryptorchidism.
A
Failure of the testes to descend through the inguinal canal to the scrotum, and so is retained in the abdominal cavity.
Causes infertility, tumours, torsion and behavioural problems.
During castration, if you can only locate 1 teste, always go back int the abdominal cavity to remove both.
3
Q
What is the spermatic cord comprised of?
A
Ductus deferens Testicular artery and vein Pampiniform plexus Testicular plexus of nerves lymph drainage Connective tissue Visceral layer of vaginal tunic
4
Q
What is the function of the mesorchium?
A
Alongside the cremaster muscle and ductus deferens, mesorchium helps support the testes.
5
Q
Describe what happens during testicular descent.
A
In the descent of the testis, they must pass through the inguinal canal to get down into the scrotum.
So during descent, as it is retroperitoneal, it stays outside the peritoneum.
During descent, the peritoneal cavity has pushes a finger-like process through the inguinal canal as well, which lies next to the testis and is called the vaginal process. The part of the peritoneum that surrounds the vaginal process is called the veginal tunica.
6
Q
Describe the structure of the vaginal tunic.
A
Made up of 2 layers:
- The inside layer closely adheres to the structures it covers at each point and it is called the visceral vaginal tunic.
- The second layer is the parietal vaginal tunic.
The gap between the layers is celled the vaginal cavity and is continuous with the peritoneal cavity.
7
Q
Name the 4 layers that must be cut through in a castration.
A
- The skin
- A smooth muscle layer called the dartos muscle
- External spermatic fascia, which is a loose connective tissue layer, which can be easily broken down in blunt dissection
- Internal spermatic fascia, which is a very strong fibrous collagenous connective tissue layer, which requires a scalpel
8
Q
Compare and contrast the 2 types of castration.
A
If you cut through the internal spermatic fascia, it opens up the vaginal process, as the parietal vaginal tunica is adhered to closely to the internal spermatic fascia. This is an open castration. If the internal spermatic fascia is intact, this is a closed castration.
Either method of castration involves breaking down some ligaments at the bottom. These are remnants of embryological structures that help the testis descend down into the scrotum.
9
Q
What is the cranial gonadal ligament?
A
Cranial gonadal ligament – at the start of testis descent, cranial gonadal ligament degenerates and descent begins.
10
Q
Describe the caudal gonadal ligament.
A
Caudal gonadal ligament/gubernaculum extends down through the inguinal ring and into the scrotum. It guides descent. It remains intact and is divided into 3 parts:
- Proper ligament of the testis – runs between testis and epididymis. Remaining parts of the ligament of the tail of the epididymis and the scrotal ligament.
- Ligament of the tail of the epididymis – this ligament is much tougher than the scrotal ligament. Broken down in an open castration.
- Scrotal ligament - broken down in a closed castration.
11
Q
Describe the canine penis.
A
- Is a musculocavernous type of penis.
- Large cavernous spaces fill up with blood during erection.
- Glans divided into pars longa glandis and bulbus glandis, involved in copulatory lock.
- Penile urethra is completely surrounded by cavernous erectile tissue called corpus spongiosum. There is a collagenous layer surrounding this called the tunica albuginea.
- Corpus cavernosa – pair of cavernous bodies dorsal to penile urethra and corpus spongiosum tissue. These ossify more distally to form the os penis, meaning the do penis is always partially erect.
- Cura attach penis to ischial arch at the root of the penis.
12
Q
How does erection occur in the musculocavernous penis?
A
- In the flaccid penis, sympathetic nerves bring about tonic contraction of the smooth muscle in the walls of the erectile tissue and the retractor penis muscle.
- In arousal, the sympathetic tone is inhibited and the smooth muscle in the walls of cavernous spaces relaxes and allows the spaces to fill with blood.
- At the same time, the muscles in the urogenital diaphragm, the ischiocavernosus, ischiourethralis and bulbospongiosus, compress venous return, trapping blood and causing swelling, increasing length and width.
13
Q
What is copulatory lock?
A
The ischiourethralis muscle contracts around the dorsal vein of the penis to stop venous return. There is also relaxation of the retractor penis muscle, which allows and increase in length.
However, there is another possible route of blood exit from the penis: the superficial vein of the glans. It is constricted by the vestibularis muscle, which is located in the bitch. So this muscle surrounds and compresses the vestibule in the female reproductive tract. This causes copulatory lock and complete swelling of the bulbus glandis here. Lock can last for 20 minutes.
14
Q
Describe the species differences in scrotum topography.
A
- In the bull and ram, the scrotum is pendulous and vertical, and the orientation of the testes is almost vertical.
- In the cat and boar, the scrotum is very caudal, almost horizontal and sub anal.
- The dog and stallion are somewhere in the middle of these two.
15
Q
How is teste conformation different between large and small animals and what are the species differences?
A
Different to small animals, the head of the epididymis is next to the pampiniform plexus and the tail is away from the pampiniform plexus in large animals.
- In general, the testes in carnivores are relatively more horizontally placed, as well as in the horse and pig. The head of the epididymis is more cranial and the tail more caudal.
- In the ruminants, because the testes are vertically placed, the head is dorsal and the tail is ventral.
16
Q
How does erection occur in the fibroelastic penis?
A
Sigmoid flexure retains penis within prepuce and bilateral retractor penis is contracted due to decreased sympathetic tone.
Engorgement restricted to sigmoid flexure, retractor penis muscle relaxes and flexure straightening, protruding from penis.
17
Q
Describe the species differences in the size and shape of musculocavernous penises.
A
Cats faces caudally and is covered with barbs to induce ovulation in the queen.
The horse penis is more complex, as it has an elongation of the urethra called the urethral process that sits in a depression called the urethral fossa. This has clinical significance.
18
Q
Describe the species differences of the size and shape of fibroelastic penises.
A
- Bull has tiny glans and a raphe that twists around
- Ram has a worm-like urethral process, which has clinical implications with kidney stones, and a bump on the left side celled the tuberculum spongiosum.
- Pig’s is long and thin but corkscrews when erect, which has implications for AI.
19
Q
What is the function of the male gonadal accessory glands?
A
There are 4 different types. Their purpose is to produce seminal fluid to facilitate motility and nutrition for the sperm. There are species variations in size, shape and presence in each animal (though all mammals have a prostate).
20
Q
Describe the accessory gonadal glands of the dog.
A
Prostate - clinically significant if old entire males get prostatitis, an inflamed prostate due to the effects of testosterone. This is not normally malignant but will cause great discomfort and problems defecating. The prostate can be palpated rectally.
Ampullae – difficult to see as they are really thickenings of the distal parts of the ductus deferens.
21
Q
Describe the accessory gonadal glands of the pig.
A
- Prostate
- No ampullae
- Vesicular glands – seminal vesicles close to the bladder.
- Huge bulbourethral glands
22
Q
Describe the accessory gonadal glands of the ox and horse.
A
Have all 4 glands, but vary in shape and size.
In the ox, most of the accessory glands are situated near the neck of the bladder.
23
Q
Describe the blood supply to the large animal male reproductive tract.
A
Internal iliac supplied the internal pudendal arteries and veins.
In horses, cranial gluteal artery and obturator artery.
24
Q
Describe the innervation of the large animal male reproductive tract.
A
Autonomic innervation due to pelvic and hypogastric nerves.
Somatic innervation due to the genitofemoral nerve and pudendal nerve.
25
In basic male pelvic blood supply, what 3 sections is blood supply split into?
* Blood supply to the penis
* Blood supply to the testis
* Blood supply to the scrotum and prepuce
25
How does the internal iliac artery supply the male pelvis?
Bilateral and supplies internal pelvic organs, penis and perineum.
- Goes deep into the pelvic cavity. 1st branch is the umbilical artery to the bladder. 2nd branch gives off the caudal gluteal artery to the guts.
- Then becomes the internal pudendal artery. 1st branch is the urogenital artery. 2nd branch is the vaginal artery, which becomes the uterine artery and anastamoses with the ovarian artery.
- Internal pudendal artery exits via the ischiorectal fossa and becomes the penile artery.
25
How does the testicular artery supply the male pelvis?
It branches off the aorta and travels through the inguinal canal to reach the testis.
26
How does the external iliac artery supply the male pelvis?
Supplies the hindlimb and exits through the femoral canal to become the femoral artery.
- Has a branch called the deep femoral artery, which gives off the pudendoepigastric trunk.
- One of the branches of the pudendoepigastric trunk is called the external pudendal artery, which goes through the inguinal canal to supply the scrotum and prepuce in the male (mammary glands in female).
- Another branch of the pudendoepigastric trunk is the caudal deep epigastric that supplies the inside of the caudoventral wall inside the body.
27
Describe autonomic innervation of the male pelvis.
* Sympathetic – exits CNS via thoracolumbar region and innervate the pelvis via the hypogastric nerves (are paired).
* Parasympathetic – cranial and sacral outflows only. Vagus does not travel the whle way to the pelvis. Sacral outflow/pelvic nerves reach pelvis.
28
Describe somatic innervation of the male pelvis.
Exits CNS via lumbosacral plexus, which is comprised of the last 5 lumbar and first 3 sacral nerves.
• Genitofemoral nerve = L3-L4 = inguinal canal
• Femoral nerve = L4-L6 = femoral canal
• Obturator nerve = L4-L5 = obturator foramen in the os coxi
• Lumbosacral trunk = L6-S2 = greater sciatic foramen and makes up a lot of
the sciatic nerve
• Pudendal nerve = S1-S3 in dogs, S2-4 in horses and cows = ischiorectal fossa
• Caudal rectal nerve may be its own nerve or be a branch of the pudendal
29
What is the function of the uterine tube?
Uterine tubes catches any oocytes that are ovulated from the surface of the ovary and convey them to the uterine horn.
It provides the correct conditions for fertilisation.
Runs between the ovaries and the tip of the corresponding uterine horn.
30
What are the 3 sections of the uterine tube?
Infundibulum – widest part near the ovary and has finger-like projections which are called fimbriae. The direct/waft ova into the uterine tube.
Ampulla – where fertilisation occurs.
Isthmus – narrowest section
31
What are the 3 layers of the uterine wall?
* Mesometrium – the outer mesentery layer supports the uterus
* Myometrium – the smooth muscle layer
* Endometrium – the inner lining of the uterus
32
What is the function of the cervix?
Acts as the junction between the uterine body and the vagina.
33
What is the structure of the cervix?
Contains a high proportion of collagen and smooth muscle fibres.
Cervical canal is very narrow and is normally closed. Can be filled with a mucus plug.
Cervical canal only opens at times of mating to allow the passage of sperm and the time of parturition, when the canal expands greatly.
Depending on species, some may have change sin the appearance of the cervix depending where they are in the oestrus cycle, caused by hormonal changes. Example: mare
34
Describe the blood supply to the uterus.
Paired arteries:
* Ovarian artery – a direct branch of the aorta.
* Uterine artery – a branch of the vaginal artery. Vaginal artery branches into smaller branches near the uterine wall to supply it. It anastomoses with the ovarian artery.
35
Name the different mesenteries that support the different parts of the female reproductive tract.
* Mesovarium – supports ovaries
* Mesosalpinx – supports the uterine tube
* Mesometrium – supports the uterus
* Pelvic fascia surrounds the distal part of the reproductive tract, vagina and vestibule. They are located within the pelvic cavity and outside of the peritoneum.
36
Describe the peritoneal attachments that support the female reproductive tract.
* There are 2 peritoneal attachments that hold the ovaries up against the dorsal body wall and are part of the mesovarium.
* There are 2 attachments that attach uterine body to the dorsolateral body wall and are part of the mesometrium.
37
Name the female gonadal ligaments.
The cranial gonadal ligament/suspensory ligament is divided into 2 parts in the female:
- The proper ligament is the part between the ovary and the tip of the uterine horn
- The round ligament runs through the mesometrium, down to the inguinal canal in the bitch
38
What is the ovarian bursa and how are they formed?
In some species, the ovaries are completely surrounded by a bag or fold of peritoneum, a pocket formed by the mesovarium and mesosalpinx.
Formed when mesosalpinx and mesovarium overlap and form a ridge tent, the bottom of which has an opening. This forms the bursa.
39
What are the 2 types of ovarian bursa?
* Closed ovarian bursa – has a very small opening so bursa completely surrounds ovary. Example: bitch
* Open ovarian bursa – very wide open pocket so ovarian surface is visible. Example: mare, cow, sow
40
What is the vestibule?
The entrance to the female reproductive tract.
41
Describe the structure of female genitalia in the cow.
- Ventral part of the vestibule is the urethral opening, at the border of the vestibule and vagina.
- Just caudal to the external urethral opening/urethral orifice, the cow has a blind ending sack called the suburethral diverticulum, which can get caught on in catheterisation.
- Cows have 2 large vestibular glands, which can be felt in a vaginal palpation as lumps either side of the urethral opening.
- The clitoris will be sitting in the ventral commissure/the most ventral part of the vestibule.
42
Describe the structure of female genitalia in the mare.
- Unlike the cow, vetsibule glands are distributed more diffusely.
- Prominent clitoris, especially in heat, and is exposed by ‘winking’ movement of the labia.
- Clitoris sits in clitoral fossa. Also has a clitoral sinus, a pocket within the clitoris itself. (This is important for Contagious Equine Metritis, in mares and stallions, CEM are STD microorganisms that may hide in the clitoral fossa and sinus. CEM can cause subfertility and abortions.)
43
Distinguish polytocous and monotocous.
Polytocous – large litters. Many follicles develop at the same time and the ovary looks like a bunch of grapes. Example: pigs (although unlikely to rectal a sow) and dogs.
Monotocous – usually one offspring but can have twins or triplets, etc. Example: cow and mare. Sheep are ditocous and have twins.
44
What are ovarian bursa?
Is a fold of mesentery formed by the mesosalpinx joining the mesovarium to form a tent where the ovary is enclosed.
In small animals, this is normally filled with fat but is easier to see and has no clinical significance in large animal.
- Dog has a closed ovarian bursa
- Cows and mares have open ovarian bursa
45
What are the 3 classifications of uteri?
Simple
Duplex
Bicornuate
46
Describe a simple uterus.
Present in humans and primates
- 1 cervix
- Massive uterine body
- No uterine horns, only uterine tubes
47
Describe a duplex uterus.
Present in rabbits and rodents
- Uteri have 2 horns that are completely separate
- Each horn has its own cervix, so there are 2 cervixes
- No uterine body present
48
Describe a bicornuate uterus.
- 2 uterine horns
- 1 cervix
- 1 uterine body
- Prominent body: mare, cat, dog
- Small body: pig, cow
49
How do length of uterine horns and litter size correlate?
Dogs and pigs have relatively large litters, so there will be foetuses all along the uterine horns and you may get one foetus in the uterine body. So long horns = large litters.
50
What are caruncles and cotyledons?
Ruminant endometrium has plug-like structures called caruncles – the sites where embryonic membranes will attach.
Cotyledons are in the placenta and will plug on to caruncles to form a placentome, where exchange of gases, wastes and nutrients occurs.
Caruncles are pigmented in the sheep but not the cow.
51
Describe the topography of the mare female reproductive tract.
- The uterus tends dorsal but more ventral in pregnancy.
- The ovaries are sublumbar.
- So, if you put your hand in for rectal exam you would put your palm facing upwards to palpate the ovaries.
52
Describe the topography of the cow female reproductive tract.
- The uterus curls down over the pelvic brim.
- The ovaries are positioned a more ventrally compared to the mare (they are attached to the dorsal wall also)
- So, you put your hand with the palm facing downwards to feel the ovaries.
53
Describe the topography of the sow reproductive tract.
It is very unlikely that you will perform a rectal exam but you will be using an ultrasound scanner.
You can see here that the sow has a sort of intermediate arrangement to the mare and cow, with the uterus projecting ventrally and the ovaries placed sub-lumbar.
54
Describe how the cervix changes in the reproductive cycles of the mare, cow and bitch.
As a mare goes into oestrus, cervix becomes swollen and inflamed.
Cow cervix does not change much during the reproductive cycle.
Bitch cervix is closed during anoestrous, dioestrous and proestrous and this is clinically significant. Pyometra is hormonally induced in the bitch and a closed cervix means infection has nowhere to go so surgery is required asap.
55
How does blood supply in large animals differ to that in small animals?
Follow the same pattern as in the small animal, but there is an extra and important blood vessel supplying the uterine horns in addition to the uterine artery called the middle uterine artery.
56
Describe the middle uterine artery and its species differences.
It is an extra blood supply to the uterus of the large animal which is additional to the uterine artery. It anastomoses with the ovarian artery (just like the normal uterine artery).
- In the mare, the middle uterine artery arises from External iliac artery.
- In pigs and ruminants, middle uterine artery arises form umbilical artery.
57
State the 2 key functions of the placenta.
* Physiological exchange of nutrients, gases and waste products
* Production of hormones
58
State the 4 foetal membranes.
Chorion
Yolk sac
Allantois
Amnion
59
Describe the chorion foetal membrane.
The outermost embryonic tissue and is associated with the endometrium of the uterus. Chorionic villi project into endometrium to bring foetal blood close to maternal blood.
60
Describe the yolk sac foetal membrane.
Taken into the embryo to form the gut tube. External parts forms a provisional placenta (choriovitelline).
61
Describe the allantois foetal membrane.
Outgrowth of the hindgut that forms the allantoic cavity. Forms the definitive/proper placenta called the chorioallantoic placenta. Allantoic cavity becomes vascularised with umbilical vessels.
62
Describe the amnion foetal membrane.
Surrounds embryo
Filled with fluid
Attached to embryo at umbilicus
63
State the 2 foetal fluids.
Allantoic
Amniotic
Found in their respective membranes
64
Describe allantoic foetal fluid.
- Volume generally increases during pregnancy
- Amount variable between species
- Extension of bladder so stores renal waste until urachus closes
65
Describe amniotic foetal fluid.
- Volume increases during earlier stages of pregnancy to protect fragile foetus.
- Decreases in latter stages when foetus us more robust.
- Stores renal waste once urogenital membrane has opened and urine is released from urethra.
66
Describe the arrangement of foetal membranes in the horse and dog.
The allantois totally surrounds the amnion so only chorioallantoic connections exist. Born totally enclosed in the amnion so must be removed to avoid suffocation. Amnion does not need to rupture, as it is not attached to the chorion.
67
Describe the arrangement of foetal membranes in ruminants and pigs.
The amnion is in connection with the chorion. Not normally born totally enclosed in the amnion, as the amnion usually ruptures, as it is attached to the chorion.
68
Describe foetal membrane arrangement in polytoccous animals.
Such as pigs, each foetus must rupture its own amniotic membrane. The only time thing will share foetal membranes is identical twinning.
69
What 2 ways are chorioallantoic placentae classified?
Gross - due to distribution of the villi of the chorion.
Histological - how many layers between the maternal and foetal blood vessels.
70
Describe the different gross classifications of placentae.
Diffuse – horse and pig. Villi are distributed randomly over chorionic sac.
Zonary – carnivores. Villi are arranged in a ring around the middle of the chorionic sac.
Cotyledonary – ruminant. Villi are arranged in multiple discs called cotyledons.
- Cow: maternal tissue has a more convex shape and so the foetal tissue attaches around the outside.
- Ewe: maternal tissue on concave and foetal tissue has to protrude into the inside of these donut shapes.
Discoidal – human (a little different) and rat. Villi are arranged in one big disc.
71
Define cotyledon, caruncle and placentome.
Cotyledon - foetal tissue
Caruncle - maternal tissue
Placentome - cotyledon and caruncle come together
72
In histological classification of placentae, what is epitheliochorial?
Maintains 6 layers
Mares
Sows
Ruminants
73
In histological classification of placentae, what is endotheliochorial?
Reduced to 4 layers
Cat
Dog
74
Describe the external anatomy of the udder.
- The skin on the udder is soft and pliable and covered with fine hair, almost velvety
- The escutcheon (shield) is on the caudal region of the udder, where the hair is directed dorsally
- The median intermammary groove divides the udder into left and right halves. The udder will also be divided into quarters, left and right cranial an caudal quarters
- In theory, you could surgically separate the left and right halves if needed, but this is rarely done, could be due to mastitis that this could be done
- In some animals, there are supernumerary teats, which are normally blind ending and non-functional. They may interfere with the milking machine so are normally removed
75
What are mammary glands?
Modified and enlarged sweat glands.
During pregnancy and lactation, the mammary gland develops by forming ducts from cuboidal epithelium with myoepithelial cells to aid excretion so the muscle will contract to move milk along the gland and towards the teat.
76
Describe the lactational secretory pathway.
1. Alveolar secretory units
2. Small interlobular ducts
3. Interlobular ducts
4. Relatively wide lactiferous ducts
5. Gland sinus/cistern - a widening area that collects and stores milk.
6. Teat sinus/cistern - separated from the tea by the annular fold, a mucosa septum, which has a central aperture and a vascular ring around the teat base.
7. Teat orifice - milk clots can from here.
8. Muscular sphincter with additional elastic fibres between the teat canal and orifice to prevent leakages.
77
Describe the change in epithelium in the lactiferous pathway.
- Alveoli, ducts and sinuses have cuboidal epithelium
- Protection is needed from abrasions and invaders as the teat canal approaches so changes to stratified squamous epithelium
- The transition between these 2 epithelia under a microscope looks like a rose so is called the rosette od frustenberg
78
Describe the suspensory apparatus of the udder.
Suspended by tough connective tissue:
- Lateral laminae envelops the udder and meets the medial part of the udder to form a double layer called the medial lamina.
- Space between the medial lamina is filled with areolar connective tissue.
- Medial lamina tissue has more elastic fibres than the lateral lamina, causing udders to splay.
- Both laminae detach lamellae that interdigitate with glandular tissue to hold it more tightly.
- Both laminae become thinner more ventrally.
79
What happens to a cow if the suspensory apparatus get damaged?
The cow will probably have to be culled as the teats will be too close to the ground and may get damaged and recurrent infections.
80
Describe the blood supply to the bovine udder.
Main blood supply is via the external pudendal artery:
- External pudendal has a sigmoid flexure emerging from the inguinal canal, which helps not stretch the artery too much when the udder is full and heavy.
- Branches into the cranial mammary artery and caudal mammary artery, which both send branches out throughout the udder.
- Internal pudendal artery will anastomose with the caudal mammary artery via the ventral perineal artery.
81
Describe the blood supply to the bovine udder.
Main blood supply is via the external pudendal artery:
- External pudendal has a sigmoid flexure emerging from the inguinal canal, which helps not stretch the artery too much when the udder is full and heavy.
- Branches into the cranial mammary artery and caudal mammary artery, which both send branches out throughout the udder.
- Internal pudendal artery will anastomose with the caudal mammary artery via the ventral perineal artery.
82
Why are there 2 main ways of venous drainage from the udder?
An adaptation of the cow so that venous return is not blocked when the cow is recumbent.
83
What are the 2 main ways of venous drainage?
The blood from the udder is drained by a venous ring above the base of the udder (there is also a vascular ring around each teat). Venous ring is drained by the external pudendal vein.
Venous ring is also drained by the ‘milk vein’, which forms in the first pregnancy when the cranial and caudal superficial epigastric veins anastomose.
84
Describe the arterial supply in the udder that veins are satellite to.
Pudendoepigastric trunk:
- Epigastric part becomes the caudal deep epigastric and travels inside the body wall
- Pudendal part becomes the external pudendal artery
Caudal superficial epigastric artery is a branch of the external pudendal artery and runs cranially subcutaneously.
85
What is the 'milk well'?
‘Milk well’ is simply the place in the thoracic area where the ‘milk vein’ enters the body cavity to drain into the internal thoracic vein.
86
Describe how the milk vein drains the udder.
Milk vein is an anastomosis of the cranial superficial epigastric vein and the caudal superficial epigastric vein. It travels subcutaneously and enters the body wall at the milk well.
Here, it drains into the internal thoracic vein and then into the vena cava.
It has bidirectional flow, as they are so wide, depending on whether the cow is laying down.
87
Describe the innervation of the udder.
- Genitofemoral nerve arises from L3&4 and reaches the udder via the inguinal canal. It supplies the mammary tissue, inner teat tissues and the skin in the middle of the udder and teats.
- Pudendal nerve arises from S2-4 and exits the ischiorectal fossa via its mammary branch. It supplies the caudal skin of the udder.
- Cranial skin is innervated by the iliohypogastric and ilioinguinal nerves.
88
Where do the urinary and reproductive tracts both arise?
Intermediate mesoderm
89
After the initial stages of development, how does the Y chromosome affect development?
Y chromosome: testis develop > testosterone produced > male reproductive tract development
No Y chromosome: no testis develop > no testosterone produced > female reproductive tract develops
90
Describe the initial stages of development of the urinary and reproductive tracts.
* Paramesonephric ducts develop lateral to the mesonephric ducts
* Mesonephric (Wolffian) ducts enter cloaca as 2 ducts in the male
* Paramesonephric (Mullerian) ducts enter cloaca as a single duct in the female
* Genital ridges appear next to mesopnephrons, which become the gonads
91
How does the epithelium of the genital ridges start to form the primitive sex chords?
Male: gene on the Y chromosome causes sex cords to develop into cords of testis. At the end of this stage of development, the tunica albuginea forms to separate cords from epithelium and become a teste on it own, not connected to the posterior wall.
Female: no Y chromosome, so the primary sex cord will start to degenerate and secondary sex cords develop. These will from the follicular cells surrounding the eggs and the germ cells from the yolk sac become the oogonia/eggs.
92
What 2 hormones do the testis begin to secrete after they have started to develop?
* Testosterone – cause the mesonephric ducts to enlarge to form the ductus deferens.
* Mullerian inhibiting hormone – degeneration of the paramesonephric ducts.
93
How does the female reproductive tract develop?
1. The mesonephric ducts regress due to the lack of testosterone.
2. The paranephric ducts develop into the female reproductive tract as there is no Mullerian inhibiting hormones to inhibit growth.
3. The caudal part of the paramesonephric ducts will form the uterine body, the cervix and part of the vagina.
4. The uterine septum will disappear, the timing of which has species variation.
5. The vagina comes from 2 parts: the upper portion from the paramesonephric duct and lower portion from the urogenital sinus, which is the same area that the bladder comes from.
94
What is Freemartinism in cattle?
Usually occurs in XX females who are born as a twin to an XY male.
- XY hormones are passed between the calves via the placenta to the female.
- Gonads may resemble ovaries or testis
- Paramesonephric duct development is disrupted, and the cranial vagina is not developed and the caudal vagina develops as a closed diverticulum.
- The clitoris is enlarged
- There is a characteristic tuft of hair at the ventral commissure of the vulva
- Mammary glands/teats are underdeveloped
95
What are the species variation of the paramesonephric ducts?
Duplex - rabbit, hamster, rat
Bipartite - some carnivores and ungulates
Bicornuate - cat, dog, ferret, ungulates
Simplex - primates
96
Describe the initial development of the external genitalia.
Initial stage is the same in males and females.
- There is a genital tubercle that develops
- There is a urogenital fold either side of the urogenital opening
- Swellings develop lateral to the folds
- Urethral groove will develop on the ventral surface of the genital tubercle
97
How does the male external genitalia further develop?
- Testosterone will cause the genital tubercle to elongate to help from the penis.
- The urethral folds will close over the urogenital opening and form the urethral groove. This forms part of the penis and the urethra will be enclosed within the urethral groove.
- The genital swellings will become the scrotum.
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Hoe does the female external genitalia further develop?
No testosterone, so the genital tubercle stays quite small and becomes the clitoris.
The urethral groove disappears and the urethral folds become the labia.
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What is hypospadias?
A condition where the urethral folds to not close properly and openings can occur at any point along the urethral development. Urination does not occur at the end of the penis and occurs in the wrong position.
