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
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
How long is an equine oestrus cycle? How long are they in standing heat? When does ovulation occur?
* Horses have an average oestrous cycle of 21 days
* Horses are in standing heat for up to a week (4-8 days)
* Ovulation happens 1 to 2 days before the end of oestrus
What is different in regards to follicles in monotocuous vs. polytocuous species?
* Monotocuous: one follicle is dominant- the largest around the time progesterone levels drop- will start secreting inhibin which has a negative feedback on FSH release from the pituitary. The larger the follicle, the less dependent it is on FSH. Also, it is getting more blood- so the largest amount of FSH.
* Polytocuous: Multiple follicles are needed to generate enough inhibin in order to exert the negative feedback on the pituitary
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
Oestrus cycle in cats?
* Cats are seasonally polyoestrus: interoestrous interval is 2 to 3 weeks in spring, summer, and autumn, followed by a time of anoestrus in winter
* Indoor cats can become non seasonal breeders with too much artificial light
Prooestrus average: 1.2 days
Oestrus average: 7.2 days
Postoestrus average: 8 to 10 days-- follows oestrus if ovulation does not occur
Dioestrus average: 40 days in pseudopregnant, 60 days in the pregnant queen-- FOLLOWS OESTRUS if ovulation DOES occur
* Ovulation without fertilization: CL develop and produce progesterone for up to 45 days, clinical signs do not occur except for a long period without oestrous signs
* Ovulation with fertilization: ova remain fertilizable for up to 24 hours post ovulation; sperm requires 2 to 24 hours after ejaculation for capacitation and remain viable for about 50 hours after ejaculation
What are the signs to look for in cattle prooestrus/ early oestrus? What is the problem?
Cows riding other cows, restlessness, vocalization. Oestrus: standing to be mounted, presence of ruffled hair at base of tail; rubbed of tail paint if used
* Problem: 70% of cows show heat between 6pm and 6am-- tail paint for heat detection devices are therefore used
For a breeding mare, what is the most important practice for determining when to inseminate or breed?
* Teasing mares from 3 days post-partum until 60 days pregnant
How can you tell if a bitch is in heat?
Serum progestone levels, breeding reflexes, exfoliative cytology, vaginal exam speculum
What are the two basic mechanisms for manipulating oestrus cycle?
Inducing luteolysis (PGF2alpha) & prolonging luteal phase (progesterone)
What are the benefits of synchronization of oestrus?
* Improved oestrus detection rate (animals should come into heat in a shorter time frame)
* Allows timed mating and AI in females in which oestrus detection is difficult
* More efficient use of AI with fresh or frozen semen in groups of animals
* Synchronization of oestrus and ovulation for embryo transfer
What do you have to have for synchronization of oestrus? What is a treatment for anoestrus? What is important to know about PGF2alpha use?
* You have to have active ovaries for synchronization of oestrus
* Anoestrus- use GnRH analogues
* PGF2alpha only works on CLs older than 5 days, also it is a potent abortifacient in most domestic species
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)
Why is horse synchronization often not very tight? Cattle too, but especially horses.
When a mare comes into heat after the 2nd PGF2alpha dose-- a mare that already has a follicle >35 mm at the time of PGF2 alpha treatment will come into heat much quicker than a mare that has only a small or atretic follicle.
What is an advantage of using progesterone to synchronize heat? What is a disadvantage? What do you often give in addition to progesterone?
* Advantage- animals do not have to have a CL at the time of treatment
* Disadvantage- long time interval between time of treatment and mating/ insemination
* since animals can have a CL present at the time of treatment, usually PGF2alpha is also given at the time of progesteragen withdrawal
What devices are commonly used in ruminants for synchronization of heat? Horses? Pigs?
* Ruminants: CIDR- controlled intravaginal drug release
PRID- progesterone impregnated intravaginal device (prolongs luteal phase- perhaps then stop it at the same time?) (in ruminants 7-10 days of treatment)
* Horses: Orally - altrenogest or injection of progesterone and oestradiol in order to suppress follicular develop to get a tighter synchronization (10-14 days of treatment)
* Pigs: oral - altrenogest (14- 18 days of treatment)
What are common methods of inducing ovulation in mares?
* This would be part of a synchronization program
* Human chorionic gonadotropins (hcG): LH like function, intravenous injection, if given at the right time (35 mm follicle with some oedema) 85% of mares ovulate between 36 and 42 hours, might not work in transition when lack of LH receptors
* GnRH analogue: Ovulation between 42 to 48 hours if given as soon as largest follicle is 30 mm- implant should be removed to prevent downregulation (commonly placed in mucosa of labia)
If ewes are to be joind outside of breeding season (spring/summer), what can be used to stimulate oestrus and to concentrate the joining?
"Ram effect" or "Whitten effect"- pheromones need to be kept 1 km from the ewes for at least one month before the start of joining. The sudden introduction of rams will result in cycling.
* if AI is to be used, teasers (vasectomised rams) can be used instead of intact rams-- equipped with a marking harness-- marks the ewes in oestrus
** major benefit is to achive a high proportion of ewes in lamb orver a short period and a more compact lambing
** more pronounced in British breeds
What is the regimen to be used to move up ovulation in mares?
Mares should be kept under a 16 hour light regimen from about 1st June= 2 month advantage in the onset of the first ovulation of the season. Mares will have their first oestrus earlier, but mares undergo 3 follicular waves of follicular growth but without the occurrence of ovulation, it is believed the amount of oestradiol in these transitional follicles is not sufficient to induce the preovulatory LH surge (=oestradiol affecting the surge centre in a positive feedback loop, not the low amounts of oestradiol in the negative feedback to the tonic center)
Site of deposition of semen of AI vs. normal semen deposition site
** number of sperm per AI dose can be greatly reduced
* Cattle- vagina- uterus (AI)
* Horse- uterus- uterus
*Sheep- vaginal- cervix (fresh) or uterus via laparoscope (frozen)
* dog- vagina- vagina (fresh) or uterus (frozen via surgery or endoscopically)
Fresh extended semen vs. frozen semen
* Fresh extended semen- even if chilled has a life span of about 2 days for horses and 7 days for pigs
* Frozen semen- can be stored in liquid nitrogen without loss of fertility for generations. Shortened life span once it is thawed. HAS TO BE MUCH BETTER TIMED AI!!
When should mares be inseminated with fresh extended semen for the best pregnancy rates? What about frozen semen?
* within 48 hours before ovulation or 6 hours after ovulation
* frozen semen- from 12 hours before up to 6 hours after ovulation
** the period of 6 hours after is determined by the deteriorating oocyte after that time
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
Why are ART used in domestic specie? What are some assisted reproductive technologies used in domestic species?
Currently used in cattle, sheep, goats, pigs, and with more difficulty in horses and dogs to produce offspring from subfertile males or females, increase the number of offspring from selected mature or juvenile females, salvage sperm or oocytes from dead or dying animals.
* Classic in vitro fertilization (IVF)- eggs and sprm are incubated together in a petri dish
* Intracytoplasmic sperm injection- eggs are collected and one sperm injected into one egg
* Gamete intrafallopian transfer- egg and sperm are transferred into uterine tube (e.g. donor egg from older mare with uterine pathologies to young mare)
* Embryo splitting- early embryos can be split to derive identical offspring (best done at 6 to 8 cell stage)
* Somatic nuclear transfer- cloning; a nucleus from a donor adult cell (somatic cell) is transferred to an egg that has been enucleated. If the egg begins to divide normally it is transferred into the uterus of the surrogate mother.
What is embryo transfer?
* Embryo transfer allows a dam to have many more offspring in a given year (genetically valuable individuals)-- ET has a much smaller genetic impact than sire selection.
* Principle is--> superovulate dam (exogenous FSH)--> dam is inseminated at appropriate time--> embryo flush is performed 6 to 8 days later--> embryos are either then transferred into a synchronized recipient or frozen for future use.
** in small ruminants the ET process is usually done by laparascopy or laparatomy-- in cattle and horses, it is done transvaginally
After your presynch in a cow, what do you do before you inseminate (AI)?
What are some key features of the avian reproductive system?
* No oestrous cycle or pregnancy
* Female has a single ovary and oviduct
* Female is heterozygous (ZW) and male is homozygous (ZZ)
* Males have internal testes
* Males have no prostate gland, seminal vesicles or penis (deferent duct acts as penis)
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 factors influence ovarian activity in an bird?
Light, moisture, nutrition (especially calcium), stress, diseases
What are the steps of ovulation in a bird?
1. Large follicle starts producing progesterone
2. Progesterone acts on Pituitary to produce LH surge
3. LH induces PGF2alpha and PGE production in follicles
4. PGF2alpha causes follicle to rupture releasing ovum
5. Progesterone induces laying behaviour
What is meant by oviposition? What happens?
Oviposition- to deposit or lay eggs
1. PGF2alpha induces muscular contractions in uterus
2. PGE causes uterovaginal sphincter to relax
3. Uterine contractions stimulate arginine vasotocin (AVT) release from pituitary gland
4. AVT stimulates uterine PG release
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
What is the buffer for a bird to maintain serum calcium?
* Medullary bone, if it is exhausted, cortical bone is used but can lead to osteoporosis if excessive loss occurs
* Vitamin D3 promotes calcium absorption and deposition from medullary bone
* a laying bird can use its entire serum calcium in 15 minutes
When does a domestic chicken reach sexual maturity? What is the the top 2 breeding cues?
What about sexual maturity of a budgerigar? Breeding cues of a budgerigar?
Sexual maturity- 5 months (18-20 weeks)
Breeding cue- light and Ca
* commercial chicken lays 330 eggs/year
* Sexual maturity of a budgerigar: 3- 4 months
* budgerigar breeding cues: rainfall and feed availability
* lays 4-6 eggs, egg every second day
Structure of the oviduct and what it makes
Factors that influence egg shell quality?
* Length of time in lay, the longer in lay the weaker the shells become due to inability to keep daily calcium levels high enough
* Increased environmental temperatures- due to lower food consumption and reduction of carbonate ions because of panting
* Egg laying time- eggs laid earlier in the morning are likely to have thinner shells (not consuming calcium at night)
* Body checked and misshapen eggs- startled birds after the egg has entered the uterus and the first layers of calcium carbonate have been laid down
* Disease- infectious bronchitis
* Drugs can influence
What happens after fertilization with development within the zona pellucida?
1. Ootid- stage when the male and female pronuclei are present in the oocyte- a lot of cytoplasm
2. Zygote- once pronuclei fuse, the oocyte is called a zygote
3. 2-celled embryo- the first cleavage generates a 2-cell embryo, whose cells are called blastomeres.
4. Morula- when more than 16 cells are formed
5. 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?
1. 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.
2. Once the endoderm finishes its growth-- yolk sac. Mesoderm starts growing outwards.
3. 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.
4. 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.
5. 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.
6. 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 are the foetus and maternal layers of the placenta in an epitheliochorial placenta?
Foetal extra-embryonic tissue layers:
* vascular endothelium of the allantois
* mesoderm (connective tissue) of the chorioallantois
* chorionic epithelium (derived from the epithelial layer of the foetal trophoblast)
Mammalian placentas have up to three maternal tissue layers:
* vascular endothelium of the endometrial blood vessels
* connective tissues of the endometrium
* epithelium of the endometrium
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
Position of mammary tissue, number of teats, and the number of glands/ducts per teat?
Which domestic animal species do males lack external teats/ nipples?
Stallions, male rates and mice due to complete regression of foetal mammary bud tissue under the influence of androgens
What are the four overlapping processes of uterine involution?
1. Myometrial contractions and expulsion of lochia (fluid derived from remains of foetal fluids, blood from ruptured umbilical vessels and shreds of foetal membranes-- sloughed surfaces of uterine caruncles)
2. Necrosis and sloughing of tissues- increase in uterin mass in pregnancy due to increases in both collagen and smooth muscle so involution associated with the reduction in these tissues
3. Repair and growth of surface epithelium
4. Removal of bacterial contamination- vulva relaxed and cervix dilated post-partum-- main mechanism of elimination by phagocytosis