Final Exam Repro 2 Flashcards
What type of gland is the udder?
Mammary gland- exocrine gland- udder is a modified cutaneous skin sweat gland. Parenchyma of each gland is subcutaneous.
What is a dug?
Another word for a collection of mammary glands- especially for those species that have more than 2 (e.g. cats and dogs)
Where are mammary glands derived from embryologically?
* Ectoderm and mesoderm
* Mammary buds form into Mammary ridges (on the skin)–> which make epidermal sprouts–> turn into little ducts–> and eventually alveoli
*** essentially bigger ducts branch, get smaller and end up at an alveolus
What determines the number of ducts per teat?
Usually the number of teats is about the same as the average litter size. How important it is the suckle rapidly– it takes longer to get it out the fewer ducts per teat
What is milk let down?
No sphincters that hold the milk in- milk is held by capillary pressure. Milk let down requires active contraction of myoepithelial cells surrounded the alveolus. These cells are particularly sensitive to oxytocin, which is produced in response to massaging of the teats and other stimuli (olfactory, auditory, visual).
What supports the udder?
How many glands, teats, orifices?
* Skin, Lateral suspensory ligament, Medial suspensory ligament (complete separation of right to left; incomplete separation of front to back)
* 4 glands, 4 teats, 1 orifice
Why does the udder need a good blood supply?
Milk is effectively a filtrate of milk, 500 L has to pass through to make 1 L of milk. 50L/day = 25000 litres of blood per day
Arterial: External Pudendal a. (inguinal canal); Ventral Perineal (Pelvic canal- minor contribution)
What is the milk vein? What other vein drains the udder? What is the venous ring?
Superficial cranial epigastric/ abdominal
* External pudendal vein also drains the udder
* Venous ring- forms during pregnancy, anastamoses of all veins, valves become incompetent
What lymphatic drainage from the udder?
2-4 mammary lymph nodes each side– superficial inguinal, then to medial iliac lymph nodes
* only become obvious in lymphoma really
Innervation of the udder in a cow
1st and 2nd lumbar nerves (skin cranially), perineal nerve (skin caudally), genitofemoral (inguinal) nerve (internal, deeper tissues)
How does milk travel from the alveoli out of the gland?
What happens to the udder during puberty?
What happens during pregnancy to the udder?
What is the last “state” of the udder?
* Puberty= More parenchyma
* Pregnancy= more secretory tissue (hormones can cause this)
* Involution= regression (if alveoli ducts stretch too much– signals them to stop producing milk)
What is colostrum? How is the quality assessed?
First milk- contains antibodies- species dependent (placental type)
* quality generally described by protein content, which is related to density
(low in carbs because neonatal gut isn’t designed to digest chopped up molecules, leaves them whole)
* lactose drives volume– and water follows it– simply an osmotic pressure thing
What makes colostrum quality? How is it measured? What species is colostrum key?
* Quality is mostly dependent on antibody content
* Quality is measured by the amount of protein through a refractometer (Brix refractometer) & Density (Colostrometer)
* horses and calves colostrum is very important in disease prevention
What is measured in milk? Normal? Abnormal?
What cells can be found in milk?
Mammary gland defences?
* cells and antibodies
* teat canal (physical barrier)
* keratin plug (physical barrier)
What causes milk production? What inhibits milk production?
Milk ejection– reflex–> vasointestinal active peptide- dopamine suppression, prolactin surge, oxytocin release= milk let down
* Inhibited by adrenaline, blocks OT release, constricts capillaries– also progesterone inhibits lactose formation and milk is not being removed
What are some types treatments and preventive drugs used in mastitis?
* Drugs instilled into udder, antibiotics instilled high into udder
* Teat sealants- keep low in teat
What contributes to mammary gland development during puberty and pregnancy?
Oestrogen, adrenal steroids, GH make ducts grow, progesterone and prolactin make alveoli form
What is important to remember about progesterone levels in pregnancy? What is the key progestagen in horses?
Massive individual differences- difficult to tell if a ‘normal’ pregnancy based on progesterone levels.
* foetal placenta in horses makes 5-alpha-pregnanes
Can it be harmful to give external progesterones?
Yes, in bitches. Not in horses.
Why is there a drop of progesterone after pregnancy? How does this happen?
“removal of the progestagen block”
Parturition, the foetus needs to come out.
* Only a few enzymes in between the structure progestrone and oestradiol
* Progesterone has to decrease, oestradiol has to increase
* Foetal cortisol produced by the foetus in response to its growth in the uterus and lack of space–> fetus is stressed–> ACTH is produced–> therefore cortisol
* Fetus needs a functional pituitary and adrenals for this to work
* fetal cortisol due to stress is what activates enzymes that converts the progestagens–> through a pathway–> oestradiol
What happens with the removal of the progestagen block?
Oestrogen goes up and A cascade of events – uterine contraction (myometrial contraction)
Why is oestrogen important for parturition?
Tract needs to be lubricated- secretions in the vagina and cervix so the fetus does not get stuck
* Initiates myometrial contractions– the more contractions you have the more the fetus is pushed towards the cervix– oxytocin (Ferguson’s reflex via cervical stimulation = oxytocin production) again leads to more contraction (positive feedback)
*
During parturition- what does PGF2alpha?
Leads to an increase in relaxin production by CL and/or placenta (depending on species). Relaxes the pelic ligaments and loosens the other tissues in the birth canal by softening the connective tissue, also in the cervix
Ferguson’s Reflex- release of oxytocin in response to contraction– oxytocin binding to its receptors. Once oestradiol is increasing, increases oxytocin receptors. All animals are sensitive to oxytocin at birth– (not other times, except horses- uterus will contract)
Why should owners take rectal temperature in bitches near parturition? Problem with temperature?
Rectal temp drops 8 to 24 hours prepartum, progesterone drops 24 to 48 hours prepartum– so you can assess serum progesterone daily in last few days (especially for elective caeserean)
* It drops because progesterone is thermogenic (same as within luteal phase- higher temperature when progesterone is high)
* Problem- if a dog has just played or gone outside on a hot day, extremely variable- under the same conditions– so if you do it twice a day, you do it when the dog is quiet resting in the morning and at night & you do it twice a day because whelping can start within 12 hours– so you might miss the drop
What happens with a single puppy?
Single puppies are often still born of end up in a dystocia. It is believed that a single puppy cannot produce sufficient ACTH and therefore corticosteroids to initiate parturition OR he might not be as stressed because there might be more space– therefore it goes past term and die in utero.
** Dogs are very sensitive with pre or post maturity– gestation time with 65 +/- 1 day. If a dog whelps one week early, the puppies will not survive. (Horses too)
B. Late-term abortions or the birth of very weak lambs
C. Fremitus in uterine arteries (can have a CL in a non-pregnant cow)
Urachus comes from the bladder– chorion is derived from trophoectoderm, not urachus
C. Urachus runs within the intra-amniotic part of the umbilical cord
A, D (anterior), F, G
B, C
Just progesterone– direct inhibitor of LH
* problem either getting pregnant or staying pregnant– do not know which
* yes it worries me because the embryo needs to travel every centimeter of the uterus, so it may not be able to get into or out of the horn with all the cysts blocking the way– so the mare won’t recognize the pregnancy– therefore PGF2alpha produced–> resulting in luteolysis.
* She will cycle regularly but cannot maintain pregnancy
* What could you do? Removing cysts- they would come back though, give exogenous progesterone
Causes of anoestrus? What is true vs. apparent anoestrus?
* Lactation, season, presence of offspring, stress, pathology, (pregnancy)
* True anoestrus is caused by insufficient stimuli, apparent anoestrus is failure to detect oestrus (silent heat- human shortcomings in detecting oestrus)
What are two triggers of seasonal oestrus? How does the largest factor work?
Photoperiod and to a lesser extent temperature
* In short-day breeder: high levels of melatonin stimualte GnRH release (small ruminants)
* In long-day breeder: low levels of melatonin stimulate GnRH release (mare)
Duration of oestrus and time of ovulation for cattle, sheep, goats, and pigs? What IS similar in ruminants and pigs NOT just on this topic?
* Ruminants and pigs have similar 21 day oestrus cycles but the duration of oestrus (standing heat) and the time of ovulation are more variable.
Duration of Oestrus/ Time of ovulation
* Cattle - 18 hours/ 10-11 hours after end of oestrus
* Sheep- 24-36 hours/ 24-30 hours after beginning of oestrus
*Goat- 32-40 hours/ 30-36 hours after the beginning of oestrus
* Pig- 2-3 days/ 35-45 hours after the beginning of oestrus
What is different about the oestrus cycle of a bitch?
* Only has an oestrus cycle every 7 months on average
* Endocrinologically, the LH surge marks the beginning oestrus (day 0)– LH surge lasts for 24-28 hours
* Plasma progesterone levels begin to increase slowly in late prooestrus but suddenly double at the time of the LH surge
* Progesterone levels stay high for 40-50 days!!
Prooestrus: average 9 days
Oestrus average: 8 days based on LH peak and first day of dioestrus
Dioestrus average: 57 days in the pregnant bitch- it is slightly LONGER in the non-pregnant bitch
Why can’t you use progesterone to determine if a bitch is pregnant?
Progesterone profile in pregnant and non-pregnant animals is very similar. Every bitch goes through pregnancy or pseudopregnancy after ovulation.
For canine pregnancy, what needs to happen after ovulation before fertilization?
Oocytes need to mature.
* Ovulation occurs approximately 2 days after LH peak and is not dependent on breeding. Canine oocytes are ovulated as primary oocytes and need to go through a phase of maturation before they can be fertilized. It takes 48 to 72 hours for them to undergo meiotic division to become secondary oocytes.
Who are the induced ovulators? What is a fun fact about one of the species?
* Camels, alpacas, rabbits, ferrets, cats- need to mate multiple times in order to ovulate
What is a common protocol for PGF2alpha administration in ruminants and horses?
Ruminants: 11 days apart
Horses: 14 days apart
** animals that were in diestrous at the time of the first dose will be expected to be at approximately seven days after ovulation and animals that were unresponsive during first treatment (in oestrus or within 5 days after ovulation) will be in dioestrus (later than day 5)
What is a common assisted reproductive technology (ART) used in chickens?
Sperm sexing by flow cytometry
** sterm with XX contain more DNA therefore they take up more dye– therefore they emit more light therefore a positive charge so an electromagnetic field will direct sperm
After your presynch in a cow, what do you do before you inseminate (AI)?
What are the different stages of follicular development called in an avian?
Immature/inactive ovary, growing ovary, active ovary
What is this?
Stigma- where the follicle normally splits to release yolk into the oviduct– if it splits in another place, numerous blood vessels will rupture resulting in free blood found in the egg
What are the steps of ovulation in a bird?
- Large follicle starts producing progesterone
- Progesterone acts on Pituitary to produce LH surge
- LH induces PGF2alpha and PGE production in follicles
- PGF2alpha causes follicle to rupture releasing ovum
- Progesterone induces laying behaviour
What happens with brooding?
tendency to sit on a clutch of eggs to incubate them- non-expression of many other behaviours such as feeding and drinking
Structure of the oviduct and what it makes
What happens after fertilization with development within the zona pellucida?
- Ootid- stage when the male and female pronuclei are present in the oocyte- a lot of cytoplasm
- Zygote- once pronuclei fuse, the oocyte is called a zygote
- 2-celled embryo- the first cleavage generates a 2-cell embryo, whose cells are called blastomeres.
- Morula- when more than 16 cells are formed
- Early blastocyst- when the morula forms, the outer cells tend to become compacted more than the inner cells. Two distinct cell populations form: the outer and inner cells. Fluid filled cavity is formed- blastocoel. Once a distinct cavity is visible, the embryo is called a blastocyst. ICM– embryo proper. Outer cells will form the trophoblast cells- give rise to the chorion.
How does the blastocyst hatch?
Cells keep undergoing mitoses and fluid inside the cavity is increasing the pressure on the zona pellucida.
* outer trophoblast cells produce proteolytic enzymes which weaken the zona pellucida
* blastocyst itself contracts and relaxes, causing pressure pulses–> leading to rupture of the zona pellucida–> Blastocyst hatches–> rapid growth
What occurs with the formation of extraembryonic membranes?
- In the blastocyst- thin lining forms beneath the ICM and grows around the blastocyst cavity= endoderm (blue). In between the embryo and the endoderm, the mesoderm (red) will start forming.
- Once the endoderm finishes its growth– yolk sac. Mesoderm starts growing outwards.
- Mesoderm keeps growing and pushes against the trophoectoderm (previously called trophoblast cells). This leads to the formation of little “wings” around the embryo called amniotic folds. The mesoderm completely surrounds the yolk sac and the aminotic folds continue growing upwards around the embryo.
- Allantois forms as an outgrowth from the embryonic hindgut. The yolk sac and developing allantois are now completely surrounded by the mesoderm. The mesoderm fuses with the cells of the trophoectoderm to form the chorion.
- The amniotic folds join above the embryo, forming the amniotic cavity right around the embryo. The chorion now completely surrounds the entire conceptus. The yolk sac is beginning to regress.
- 2 sacs are enveloping the embryo (amnion and chorion). Both are formed by trophoectoderm and mesoderm. The allantois continues to expand and will fuse with the chorion to form the allantochorion/ chorioallantois.
Length of stages of parturition each species
What is the hypothalamic pituitary gonadal axis?
Negative feedback loop
What hormones influence the follicles?
What about at this stage?
Gonadotrophins- FSH and LH (from the pars distalis of the hypophysis cerebri)
* Membrana granulosa cells possess FSH receptors and in later tertiary follicles, LH receptors
* LH acts on the theca interna endocrine cells to facilitate production of androgens–> passed into the membrana granulosa as substrate for the membrana granulosa cells to produce oestrogens under the influence of FSH–> oestrogen creates a favourable local environment, acts on the reproductive tract and causes the signs of oestrous
What are the large and small luteal cells derived from?
What do these cells secrete and what do those secretions cause?
Membrana granulosa cells and- large luteal cells
Small luteal cells- theca interna cells
** following follicular rupture
** The luteal cells secrete progesterone, which suppresses follicular development and promotes uterine secretion and the formation of the placenta. These cells may also produce oestrogens, oxytocin, and relaxin.
What is the corpus albicans?
CL degenerates if there is no pregnancy or at the end of gestation due to PGF2alpha released from the uterus–> capillaries degenerate and the luteal cells accumulate large lipid droplets and then degenerate–> debris being phagocytosed by macrophages–> a fibrous connective tissue scar replaces the luteal cells as they degenerate (CORPUS ALBICANS)–> gradually shrinks over successive cylces and eventually disappears
What do endometrial glands secrete? What causes an increase in growth, what about secretion?
Oestrogen causes gland growth and some increase in secretion
Under the influence of progesterone- secretions of the gland is markedly increased- HISTOTROPH which supplies nutrients to the conceptus
From day 19-21 to day 15-18 what are the ovarian and uterine changes during the estrous cycle in the cow? Due to what predominating hormones?
Histologically what are the two most obvious layers that surround the testis?
Tunica vaginalis and tunica albuginea
What are these? What percentage of pregnancies are lost at these stages? Why?
Zygotic and embryonic losses are common - 15-30%
* Chromosomal abnormalities induced by age of gametes and structural mutations induced by radiation, drugs/toxins, viruses
* Toxins- including administered drugs
* Venereal infections with bacteria e.g. Campylobacter fetus ssp venerealis or protozoa- Tritrichomonas foetus
* Failure of implantation- including pre-existing abnormalities of the uterus e.g. endometritis, endometrial fibrosis
What is the syncytium?
A layer of caruncular epithelium in which cell boundaries are difficult to define
** Binucleate trophoblast cells- produce placental lactogen. These binucleate trophoblast cells invade the maternal endometrium and often form syncytia with the epithelial cells (trinucleate cells).
What do alveolar epithelial cells secrete? What mode?
Alveolar epithelial cells secrete lipid and casein (milk protein)– lipid by apocrine mode; casein by merocrine mode
Sertoli Cell Tumour- well circumscribed, firm, white and criss-crossed by bands of fibrous tissue. 1/3rd can be functional and induce feminisation syndrome (testicular degeneration and atrophy, penile atrophy with a pendulous prepuce, hyperplasia, squamous metaplasia of the prostate, bilaterally symmetrical alopecia, gynecomastia (enlarged breasts))
** common in retained testicles in dogs
Leydig cell tumour- Well-dermarcated and tan-brown, often with multiple foci of haemorrhage. Some may be functional and produce testosterone or oestrogenic substances.
Most common in the dog, bull and cat
Seminoma- spermatogonial cell origin. Most common in aged stallions, second most common in dogs.
* more often develop in retained testicles
* Soft, homogenous, white to pink-grey masses with a bulging cut surface that may seap a milky film when squeezed (think sperm!!)– grossly resemble lympoma masses
Teratoma- totipotential primordial germ cells most often diagnosed in cryptorchid testes in young colt foals. Large and cystic or polycystic and may contain bone, mucus, hair, or even teeth. Well-differentiated and benign.
A- umbilical arteries
B- urachus
Position of mammary tissue, number of teats, and the number of glands/ducts per teat?
