Reproductive System Flashcards
Why is meiosis called reduction division
Because total number of chromosomes in the cell is halved
Define spermatogenesis
To create spermatozoa
True or false
Spermatozoa are created continuously throughout life
True
Describe spermatogonia
Large cells on the outer most parts of the seminiferous tubules (germinal epithelium)
Is diploid
First divides by mitosis into one spermatogonia and one primary spermatocyte (both still diploid)
Describe the primary spermatocyte
First duplicates it’s DNA to produce double chromosomes
Then divides by meiosis to produce 2 secondary spermatocyte (both haploid)
describe the secondary spermatocyte
Divides by mitosis or meiosis depending on source
Two secondary spermatocyte each divide into two haploid spermatids (4 spermatids total for one primary spermatocyte)
During spermatogenesis, where does the cell move
Closer towards the lumen of the seminiferous tubules
What are spermatids supported by until they develop flagellum
Supporting cells
What are spermatids considered once they develop flagellum
Spermatozoa
When the spermatids are free in the lumen of the seminiferous tubules, where are they transported for maturation
The epididymis
What happens if spermatids are not ejaculated
They die and get absorbed by the lining of the epididymis
Name and describe the parts of a sperm cell
Head: contains a nucleus with the chromosomes covered in a cap-like structure called the acrosome (contains enzymes to help penetrate ovum)
Body/mid piece: contain mitochondria to create ATP to power flagellum
Flagellum: contractile proteins to enable movement
describe the sex chromosomes of a sperm cell vs a ova
Sperm cell: a male with two copies of the sex chromosomes, XY, the haploid sperm cell can be either X or Y
Ova: a female with two copies of the sex chromosomes, XX, the haploid ova can only be X
Who determines the sex of the offspring
The male, since they contribute either an X or a Y chromosome
What do you look at with a semen evaluation and what is it used for
Typically used for large animal medicine to determine fertility
Look at: Volume produced Concentration of sperm in semen Motility of sperm Live:dead sperm ratio Morphology of sperm (deformities or defects)
What are primary defects of sperm
Occur during spermatogenesis and include heads that were doubled, misshaped, enlarged or shrunken and mid pieces that are kinked, twisted or doubled
What are secondary defects of sperm
Occur at any time from storage in the epididymis until the slide is made. Includes headless tails, tailless heads, and bent tails
LESS serious
What has the greatest effects on fertility
The total number of normal sperm or the percentage of abnormal sperm
To total number of normal sperm
As much as ____% of spermatozoa will be abnormal in a healthy animal
10-20%
Define oogenesis
To create oocytes
True or false
Oogenesis is a continuous process
FALSE
Most of the development of primary oocytes occurs ___ birth
Before birth
True or false
Females have a predetermined number of primary oocytes that she will have for life and will not make any more
True
Predetermined before birth
Primary oocytes are immature, and only develop to mature ova when the follicle they are resting in ___
Develops to maturity
Follicles mature in response to
FSH
How many follicles develop in animals that have only one offspring, why?
One follicle at a time
Because the dominant follicle suppresses the development of other follicles
How many follicles develop in animals having more than one offspring
Multiple
Maturation of a diploid primary oocyte involves it undergoing meiosis to produce a
Haploid ovum
Describe the process of oogenesis and maturation of a primary oocyte
The primary oocyte duplicated each chromosome to have double sets
The primary oocyte then divides by meiosis (1), the duplicated chromosomes pair up and then separate into 2 haploid secondary oocytes with duplicated chromosomes
The secondary oocytes divide by meiosis (2) to create haploid cells with single chromosomes. After both secondary oocytes divide, only one new division creates one ovum, and the rest are 3 polar bodies which is a remnant of the unwanted nuclear material which get broken down by the body
How many ova a created for each primary oocyte
1 ova and 3 polar bodies
What do the testes consist of
A mass of seminiferous tubules surrounded by a heavy fibrous capsule
What are the testes the site of
Spermatogenesis
What are the 3 main functions of testes
Spermatogenesis
Hormone production
Delivery of spermatozoa to the female
Describe hormone production in the testes
Interstitial/Leydig cells: stimulated by LH from the anterior pituitary, release androgens (mainly testosterone) responsible for male secondary sex characteristics
Sertoli cells (support cells): produce small amounts of estrogens stimulated by FSH.
What do Sertoli cells also do
These are the “nurse cells” for maturing spermatids -help shield the spermatocyte from attack by the body’s immune system
Describe the structure of the testes from innermost later to the outermost layer
Seminiferous tubules: site of spermatogenesis -interstitial cells located in connective tissue between the tubules
Capsule: encloses the testes in a fibrous connective tissue capsule called the tunica albuginea. Protects and supports soft contents of the testes -gives shape
Vaginal tunics: double layered sleeve of peritoneum which lines the scrotum and inguinal canal. Thin Inner layer (visceral tunic) tightly adhered to the testes and spermatic cord. Thick outer layer (parietal tunic) forms a fibrous sac around the testes and spermatic cord (lines the Corium) these tunics are separated by a small amount of fluid
Describe the descent of the testes into the scrotum
Testes begins in the abdominal cavity near the kidneys
Under the influence of testosterone, they move caudally through the inguinal canal in the peritoneum
Guided by the gubernaculum: a fibrous cord that extends from the testis to the scrotum (fails to lengthen or actively shortens to pull testis down)
As the testis pushes through the peritoneum of the inguinal canal, it creates the vaginal tunic
Eventually completely passes into the scrotum and descent in complete
Describe when testes drop in different species
Ruminants: prior to birth
Pigs: just before birth
Horses: around time of birth
Cats/dogs: shortly after birth (days to 8 weeks)
What is the scrotum and what does it do
A sac of skin which houses the testes
Functions to thermoregulate and provide a favourable environment for production of sperm
How does the testes thermoregulate
The testes is raised and lowered via the cremaster muscles depending on environmental temperatures.
In hot temperatures the muscle relaxes and the testes hangs low
In colder temperatures the muscle contracts and raises the testes
What is the spermatic cord
A group of structures which extends proximally from the testis through the inguinal canal
Includes: blood and lymphatic vessels, nerves, and the vas deferens covered in an extension of the vaginal tunic
Links the testes with the rest of the body
Describe the cooling mechanisms of the blood vessels within the testes
The pampiniform plexus
A complex of veins wrapping around the arteries of the testes
Veins carry cooler blood than arteries since it just returned from the skin, heat transfer occurs to cool arterial blood and warms the blood in the veins returning to the body.
It is an example of a countercurrent exchange
Helps keep the testes at suitable temperatures for spermatogenesis (cooler than body temp)
What is the epididymis
An elongated highly coiled organ that lies next to the testes and receives immature sperm from the seminiferous tubules
It is the site of maturation for sperm
Where does the head, body and tail of the epididymis attach
The head attaches to the same end of the testes that the spermatic cord enters
The body parallels the long axis of the testis
The tail continues as the ductus deferents which doubles back along the body of the epididymis to the region of the head and becomes part of the spermatic cord
What moves sperm into the ductus deferens at ejaculation
Peristaltic contractions
True or false
The epididymal duct is very long
True
What is the ductus deferens/ vas deferens
A muscular tube that transports spermatozoa from the tail of the epididymis to the ejaculatory ducts at ejaculation
Leaves the tail of the epididymis and passes through the inguinal canal as part of the spermatic cord and eventually loops around a ureter as it continues past the bladder towards the urethra
What happens to the ductus deferens at the bladder
Thickens to form the ampulla in some species
What happens to the ductus deferens at the inguinal ring
Turns caudally separating from the vascular and nervous parts of the spermatic cord
What is the inguinal canal
In the abdominal wall, it extends from the deep inguinal ring to the superficial ring
The spermatic cord passes through this ring and the testes pass through it on its descent
What do the ampullae, vestibule glands, prostate glands and bulbourethral/Cowper’s gland all have in common
Produce the greater part of the ejaculate
Serve as transport for spermatozoa, a nutrient source, and a buffer against the acidity of the female genital tract
What is the ampullae
A glandular enlargement of the terminal parts of the ductus deferens that contributes fluid to semen
What is the vesticular gland
Paired and positioned at the neck of the bladder, join the ductus deferens to form an ejaculatory duct into the pelvic urethra
What is the prostate gland
Present in all domestic species, it more or less completely surrounds the pelvic urethra
Consists of a body (seen on outside of urethra) and a glandular layer in the urethral wall
Produces alkaline secretion that gives semen its odour
What is the bulbourethral (Cowper’s) Gland
Paired glands present in all domestic species except for the dog (lies near the bulb of the penis)
Secretes a mucus containing fluid that helps lubricate the urethra
Each gland has an excretory duct which joins the urethra
What is the anatomy of the penis
Specialized and complex organ that surrounds the terminal part of the urethra and functions in both reproductive and urinary systems
Divided into: glans/pre extremity, body or main portion, and two cura or roots (connective tissue attachment of the penis to the pelvis)
What are the two classifications of types of penises based on the amount of connective tissue present
Fibroelastic: (pigs and ruminants) High levels of connective tissue making them more firm even when not erect, non expandable, often contain a sigmoid flexure
Musculocavernous: (canine, feline, horses) lots of erectile tissue and little connective tissue so erection increases length and diameter
How is the cat’s penis modified to aid in mating
Cats have cornified “hooks” to improve attachment/hold while mating
Explains why queens scream when toms pull out
Describe the penis of the dog
Has an os penis (bone within the penis) and the bulb of the glands that causes dogs to “tie” after mating
Explain the “tie” when two dogs mate
Occurs when muscles of the vagina and vulva contract around the swollen bulb of the glands (bulbus glandis)
Causes male and female to be locked together for 15-20 minutes
Not painful -dogs will stand tail to tail until release
Improves conception rates
What is a sigmoid flexure
S-shaped curvature in the non-erect penis of the bull/ram/boar since they have fibroelastic penises
Due to their inability to swell/enlarge during erection, the sigmoid flexure instead straightens in response to increased blood pressure and the penis extends
Once erection is done, the retractor penis muscle pulls it back into normal resting S shape
What stimulates erection of the penis
Parasympathetic nervous reflex in response to sexual stimulation
Primarily pheromones
How does erection work
The penis fills with blood due to Dilation of the arteries and compression of the venous return due to the ischiocavernous muscles pressing the root of the penis cells against the brim of the pelvis
What are the two stages of ejaculation
Movement of spermatozoa and fluids from accessory glands to pelvic portion of the urethra (bladder closes to prevent semen from entering the bladder)
Rhythmic contractions of urethra pump semen out and into the female
What is the prepuce
Invaginated fold of skin surrounding the free extremity of the penis
What are the main muscles of the male genitalia
External cremaster muscle
Urethral muscle
Bulbospongiosus muscle
Ischiocavernous muscle
Retractor penis muscle
What does the external cremaster muscle do
Passes through the inguinal canal running beneath the parietal vaginal tunic, raises and lowers the testes depending on temperature
What does the urethral muscle do
Surrounds the pelvic portion of the urethra where it transports urine or seminal fluid distally by peristalsis
What does the bulbospongiosus muscle do
Continues the action of the urethral muscle in emptying the returns by peristaltic contractions
What does the ischiocavernous muscle do
When these muscles contract they pull the penis against the pelvis aiding erection by shutting off much of the venous drainage from the penis
What does the retractor penis muscle do
Following erection, this pulls the flaccid penis back into the prepuce
What artery supplies the testes
Testicular artery, branches directly from the aorta
True or false
It is easy to use local anesthetic in the scrotum due to extensive venous network
True
What does the pudendal artery supply
Penis, bladder, urethra and accessory sex glands In the bull, ram, boar and dog
What artery supplies the penis of the horse
Obturator artery and the external pudendal artery
Nerve supply to the testes is mainly supplied via the
Autonomic nervous system
Scrotal sacs are pendulous in
Dogs horses and ruminants
Scrotal sacs are not pendulous and located just central to the anus in
Cats and pigs
Vesticular glands are not present in
Cats and dogs
Describe a canine penis
Musculocavernous
Has an os penis
Glands penis (free end): divided into long part of the gland distally and bulbus glandis (engorges at erection and along with vestibular glands bulbs of the bitch is responsible for the “tie”)
Describe the feline penis
Musculocavernous
Directed caudoventrally (most others are cranioventrally)
Gland penis is covered with cornified, epithelial, proximally projecting spines
Describe the equine penis
Musculocavernous
Upon erection it expands in all dimensions so much, it deposits semen directly at the cervix
Has short urethral process that form a diverticulum dorsal to the urethra which collects smegma and debris to form a “bean” (need routine sheath cleaning)
What is smegma
Secretion of sebaceous glands consisting mainly of dead epithelial cells
Describe the bovine penis
Fibroelastic
Has sigmoid flexure
Twisted glans penis as well as a free extension of the urethra called the urethral process
Describe the porcine penis
Fibroelastic with sigmoid flexure
Twisted glans penis in “corkscrew” configuration
Prepuce: has preputial diverticulum opens dorsally to the prepuce (decomposing urine and debris collects here and is responsible for odour of pigs)
What is cryptorchidism
Failure of one or both testicles to descend (remain in abdominal cavity or inguinal canal)
May produce hormones but usually no sperm (from being kept too warm)
Hereditary in equine and porcine
Animal may be referred to as “ridgling” or “rig”
May be hereditary in dogs and cats
What are testicular tumours
Sertoli cell tumors produce estrogen, changes in behaviour and feminization occurs (pendulous prepuce, mammary gland development and milk production)
The penis and opposite testes will atrophy and other male dogs may be attracted to the animal
Why is castration done
To control sexual behaviour and aggression
What is an open castration
The scrotum and parietal tunic are incised and the testicle is removed
Suture is made to close off the communication to the abdominal cavity
What is a closed castration
Scrotum is incised, tunic is left intact
Vessels are ligated by placing sutures around the outside of the parietal tunic
Testicles are removed within their tunics
What are the risks for both open and closed castration
Infection
Herniation
Hemorrhage
Open castration Carry a greater risk of
Herniation and infection
Closed castration carry a greater risk of
Hemorrhage because it is difficult to tightly tie off vessels
What is a inguinal hernia
If the internal ring and canal are too relaxed, a loop of intestines may pass through the canal into the scrotum producing an inguinal hernia
Hereditary/more common in horses and pigs
What can happen to the prepuce with a stricture of the preputial orifice
Inability to extend the penis from the prepuce
What can also go wrong with the prepuce
Adhesions, tumors, hematomas, and congenitally short penis or retractor penis muscles and prolapse of the prepuce
May need circumcision to correct
What problem is common with prostate
Benign prostatic hypertrophy is common in older intact males
Can develop prostatic tumors or abscesses
What is the reproductive tract of the female suspended in
In a sheet of peritoneum called the broad ligament attached to the dorsal body wall
Carries blood vessels, nerves and lymphatics to the reproductive organs
At the cranial ends is the suspension ligaments of the ovary
The round ligament of the uterus is located within the broad ligament and extends caudally from the uterine horn to the inguinal canal
What are the subdivisions of the broad ligament
Mesovarium: cranial part of the broad ligaments which supports the ovary
Mesosalpinx: supports the oviducts
Mesometrium: supports the uterus
What is the primary organ of reproduction for females
The ovaries
What are the functions of the ovaries
Production of ova
Hormone production
What hormones do the ovaries produce
Estrogen: produced by developing follicles (physical and behavioural changes for breeding/pregnancy)
Progestins: primarily progesterone produced by the CL (prepares uterus for implantation and maintains pregnancy)
What two hormones affect the ovarian cycle
FSH: stimulates primary oocyte to develop into a follicle
LH: Stimulates ovulation
What are uniparous species
One oocyte released per cycle and one offspring
Horse/cows/humans
What are multiparous species
Multiple oocytes released per cycle to have a litter
Dog/cat/pig
What are the stages of the follicle
Primordial follicle
Primary follicle
Growing follicle
Mature follicle
Ovulation
Corpus luteum
Describe the first step of the ovarian cycle: primordial follicle
Immature oocyte surrounded by a single layer of follicular cells
Many found in the ovary
Some may develop into a primary follicle
Describe the second step of the ovarian cycle: primary follicle
Activated by FSH, the primordial follicle begins to develop further, follicular cells change shape from flat to cuboidal (called granulosa cells) Now called a primary follicle
Only a few follicles respond to the FSH wave Called follicular recruitment/activation
Will then continue to develop and is called a “growing follicle”
What happens to other follicle that begin to develop in uniparous species
Only one follicle will become dominant and it will prevent the others from being able to develop and they will regress and degenerate
Called follicular atresia
Describe the third step of the ovarian cycle: growing follicle
Follicular cells continue to multiply and create several layers around the oocyte
Now called a secondary follicle (with several layers)
This secondary follicle now produces estrogen in prep for breeding and pregnancy
What happens as the follicle increases in size
Estrogen levels increase
Develops a fluid filled space between the oocyte and the granulosa cells (antrum)
Primary oocyte divides to produce a secondary oocyte
Describe the fourth stage of the ovarian cycle: mature follicle (graafian follicle)
Large blister like structure in the ovary
At maximum estrogen production this stimulates LH release
The oocyte is now sitting in a stack of granulosa cells called a cumulus oophorus and is covered by a thin layer of granulosa cells called the corona radiata which acts as a barrier to insemination
Describe the fifth stage of the ovarian cycle: ovulation
Rupture of the follicle in response to the LH surge -releases secondary oocyte/immature ovum
Follicle fills with blood which clots and form the corpus hemorrhagicum
Describe what stimulate ovulation in most species, spontaneous ovulaters and induced ovulaters
Most: LH levels
Spontaneous: ovulate at predetermined times
Induced: stimulation by copulation (cats/ferrets/rabbits)
Describe the sixth stage of the ovarian cycle: the corpus luteum
Continued levels of LH change the corpus hemorrhagicum: granulosa cells continue to multiply and it develops into a large yellow mass of cells called the corpus luteum (yellow from blood)
The corpus luteum produces progestins (progesterone) to prep for implantation and pregnancy
If the LH levels do not maintain (no fertilization/implantation) the corpus luteum will regress
Describe the oviducts
Paired convoluted tubes that extend from the tips of the uterine horns
They capture and transport ova from the ovary to the uterus and serve as the location for capacitation and fertilization
Composed of smooth muscle lined with highly folded mucous membranes and covered in cilia (aid it moving ova and sperm)
Describe how the oviducts are connected to the ovaries
NOT actually attached to the ovary
The oviduct has a funnel shaped end (called the infundibulum) that is near the ovaries that catches the ovulated oocyte
How do ectopic pregnancies occur
Ovulated oocytes are caught in the in infundibulum but occasionally oocytes can sneak out of the infundibulum and implant somewhere in the peritoneal cavity (usually disintegrate but can cause implantation of a fertilized ovum elsewhere)
Describe the uterus
A hollow, muscular Y shaped organ that receives the fertilized ovum, nourishes and houses developing embryos and expels the mature fetus through the birth canal
Forms part of the placenta
Major components: body, uterine horns and cervix
What does the thickness and vasculature of the mucous membranes lining the uterus depend on
Hormonal changes and pregnancy
Describe the cervix
Projects caudally into the vagina, it is a smooth muscle sphincter that is tightly closed except at parturition and estrus
Explain why it may be difficult to treat uttering infections due to the cervix
The cervix has small pouches on either side of the opening which are easily mistaken as the opening to the uterus when using a probe to deposit medications
True or false
Mucous may be discharged from the cervix or expelled from the vulva at estrus or prior to parturition
True
When does mucous production by the cervix increase and why
During pregnancy to prevent infections from entering the uterus
True or false
the cervix also protects the vagina, making the uterus and the vagina sterile
FALSE
the cervix only protects the uterus, the vagina is NOT sterile, the uterus is sterile
Describe the vagina
Muscular tube that contains mucus glands for lubrication
Extends from the cervix to the vulva
It is the female copulatory organ and part of the birth canal
What is the vulva composed of
Vestibule: caudal part of the tubular portion of the reproductive tract common to the urinary and reproductive systems
Clitoris: the female counterpart of the penis and is located on the floor of the vestibule
Labia: forms the external boundary of the vulva
Where does the urethra enter the reproductive tract
At the junction between the vagina and vestibule
What is the estrus cycle
Defined as the time from the beginning of one heat period to the beginning of the next
Describe how the estrus cycle is controlled
Controlled by FSH and LH from the anterior pituitary gland
These hormones stimulate production of estrogens from developing follicles and progesterone from the corpus luteum
What does estrogens and progesterone do
Estrogen: physical and behavioural changes of estrus
Progesterone: prepares for and maintains pregnancy
Time of breeding depends on
The estrus cycle of the female (males are ready to breed at any time because sperm are produced continuously)
When are estrus cycles naturally timed to occur
Times to coordinate with seasons of food abundance to give greater reproductive success
Can be stimulated by environmental changes such as increasing length of days or temperature
Describe the classification of the estrus cycle according to the number of cycles per year and give an example of each
Polyestrus: cycle continuously if not impregnated (pigs and human)
Seasonally polyestrus: seasonal variations in cycling, continuous at some times of the year and absent in others (horses/sheep/cats)
Diestrus: 2 cycles per year, usually spring and fall (dogs)
Monestrus: one cycle per year (fox/ferrets/mink)
What are the 5 stages of the estrus cycle
Proestrus
Estrus
Metestrus
Diestrus
Anestrus
What happens in proestrus
Follicular development in response to FSH
increasing estrogen output from follicles cause physical prep for ovulation and breeding, thickening/development of the lining of the oviduct/uterus/vagina and the vagina develops a cornified layer to protect from trauma
What occurs at estrus
Period of sexual receptivity (peak estrogen levels)
LH release and inhibition of FSH (follicles are mature)
Ovulation normally occurs at the END of estrus
Explain what happens during estrus in induced ovulators if they are not bred
How do you treat it
(Cats and ferrets)
Will have a prolonged estrus cycle if not physically bred/stimulated
Unwanted behaviours and discharge from vagina during heat will continue up to 2 weeks (ends when the follicle regresses)
Hormonal injections, Q tip stimulation, or spaying (preventative)
Why is a prolonged estrus cycle more serious in ferrets
High levels of estrogen cause life threatening anemia (non breeding females should be spayed)
Describe what happens during metestrus
The corpus luteum develops after ovulation in response to LH acting on the empty follicle
Produces progesterone (thicken uterine lining in prep for implantation) and inhibits follicular development
Describe what happens during Diestrus
Corpus luteum is at max size and effect, if pregnant, the CL will be retained in response to continued LH levels, if not the CL will degenerate
What happens if CL degeneration is delayed even if the animal is not pregnant
Common in intact bitches
Progesterone levels will continue to prepare the body for pregnancy and can result in a pseudopregnancy (false pregnancy)
Animals develops enlarged mammary glands, may lactate, pelvis may relax, and will see mothering and nest building behaviours
Most will resolve on its own, may need hormonal treatment
Describe what happens during anestrus
Ovarian inactivity between breeding cycles in all but polyestrus species (these would continue a new cycle)
How do females attract males when ready for mating (during heat)
Pheromones
What is copulation
The physical act of breeding
Where is semen typically deposited in most species at ejaculation? Where is it deposited in horses and pigs
Most: upper portion of the vagina
Pigs/horses: deposited directly in the uterus/at the cervix
How do sperm move
Active swimming (flagellum)
Propulsive contractions of the uterus and oviducts (stimulated by oxytocin from climax and prostaglandins in semen)
Ciliary action in the oviducts
How long does it take for sperm to reach the upper parts of the oviducts
1 hour
How long can sperm typically survive in humans? What about some other species?
Humans: 72 hours
Others: 1 week
What is capacitation
The changes that sperm undergo to prepare them to fertilize the ovum
Occurs in the oviduct (sperm spend some time in here)
Includes: exposure of enzymes in the acrosome which assist spermatozoa in penetration of the oocyte
True or false
Many sperm can penetrate the oocyte
Explain how this works
False
Eggs are released when spermatozoa are fully capacitated, and they only allow one sperm to fully penetrate (when this occurs the surface of the oocyte changes to prevent others from penetrating)
Many sperm aid in penetration by use of acrosome enzymes (at the same time, the secondary oocyte changes to a mature ovum)
What is the sequence of breeding to fertilization
Breeding (before ovulation)
Capacitation
Ovulation
Fertilization
What happens after fertilization of the egg
Pronuclei of the male and female sex cells (haploid) join to create a diploid fertilized ovum/zygote
Zygote continues to divide and in a few days forms a solid mass of cells now called a morula. (All the while the zygote is moving down the oviduct)
The morula then develops a cavity and is now considered a blastocyst which will implant in the uterus
Describe a blastocyst
Has an outer layer called the trophoblast (which will develop into the fetal placenta)
And has a inner cell mass that will develop into the embryo
Has a hollow cavity that holds the inner cell mass called the blastocoele
Describe how the blastocyst implants Onto the endometrium
Creates a small pit by secreting enzymes that dissolve a small piece of the uterine lining, attaches into this pit
How many implantation sites do multiparous species have
Many sites along the horns and body of the uterus
Describe how the blastocyst eventually forms the fetus
Trophoblast: forms the fetal placenta
Blastocoele: forms the space in hollow organs
Inner cell mass:
1: ectoderm: the outer cells, form the integumentary, sense organs and nervous system
2: endoderm: cells on the blastocoele side, form the epithelium of the pharynx, lower RESP tract, GIT and bladder/urethra
3: mesoderm: middle cells between the ectoderm and endoderm, will spilt into 2 layers with a cavity between them to form connective tissue, bone, cartilage, muscle, blood/lymph vessels and kidneys
When is the embryo considered a fetus
When the various organs and organ systems have been formed
When does the fetus become a neonate
At parturition
What are teratogens? Describe what they can be, the effects of them, and what occurs at which stages
Teratogen: anything that causes defects in the embryo/fetus
Can be: genetic, infections or environmentally toxic
Effects: death, abortion, malformation, growth retardation
Times:
In early pregnancy: most susceptible, often causes abortions
During organogenesis: (first trimester) causes major developmental problems
When is the fetus more resistant to teratogens
In later stages when the organs are made
What does the development of the placenta allow
Increased nutrient and waste exchange from the mother
Acts as the life support system for the fetus
Describe the placenta
Multilayered, fluid filled membranous sac that forms around the embryo, connected to the embryo via the umbilical cord and connected to the mother via placental attachments
Is the site for nutrient and waste exchange
True or false
The fetus’ and mother’s blood mix to encourage nutrient and waste exchange
FALSE
Their blood never mixes, runs very close to each other to allow diffusion and exchange of nutrients and waste
Describe the layers of the placenta/different sacs
Amniotic sac: surround the fetus, fetus floats in the amniotic fluid as protection
Allantoic sac: sac for fluid and gas exchange between the fetus and mother
Chorion: attaches to the uterine lining and linked to the fetus via then umbilical cord
The allantochorion is the ___ part of the placenta
fetal part
What does the umbilical cord contain
2 umbilical arteries: Moves waste away from the fetus to the placenta
1 umbilical vein: carries oxygen and nutrients from the placenta to the fetus
Urachus: tube draining fluid from the fetal bladder into the allantoic sac
True or false
The fetus forms true urine
False
Not true urine, just a byproduct of the developing kidneys
What is a diffuse attachment of the placenta to the uterus, give an example of animals with this attachment type
Loosely attached sites throughout the placenta, detaches easily and completely
Horses and pigs
What is a cotyledonary attachment of the placenta to the uterus, give an example of animals with this attachment type
What is the risk with this type of attachment
Many small, button like sites called placentomes
Placental half: cotyledon
Maternal half: caruncle
Very strong attachment formed by interdigitation of the cotyledon and caruncle
Ruminants, cows, sheep, goats
Can have a retained placenta due to incomplete detachment leading to life-threatening Metritis
What is a zonary attachment of the placenta to the uterus, give an example of animals with this attachment type
Chorion form a belt shaped structure around the middle of the placenta
Usually detaches easily and completely
Dogs and cats
What is a discoid attachment of the placenta to the uterus, give an example of animals with this attachment type
Disc shaped attachment sites
Humans, primates, rabbits, rodents
What is gestation period
The time from fertilization to delivery of the fetus
Describe the 3 periods/trimester of pregnancy and what occurs in each
First trimester: fertilization/implantation/ placenta formation/ early cellular organization (embryo)
Second trimester: fetal development period: differentiation into all different body tissues and organs (basis for different systems) (fetus)
Third trimester: fetal growth period: dramatic growth, preparation for survival after delivery (fetus)
What is parturition triggered by
Size and weight of the uterus and hormonal changes
What are the hormonal changes that occur to stimulate parturition in order
1: increased glucocorticoids from the fetus
2: uterus/placenta respond by increasing estrogen and PGF2-alpha causing luteolysis and make uterus sensitive to oxytocin
3: decrease in progesterone due to CL regression -allows uterine contractions and circulating progesterone converts to estrogen
4: oxytocin release from posterior pituitary which stimulate myometrial contracts and the onset of labour
What are the 3 stages of parturition
1: uterine contractions (no abdominal pushing) presses the fetus against the cervix causing dilation. See changes in behaviour to prepare for birth
Water breaks to mark the END of stage 1 and start of stage 2
2: strong uterine contractions and abdominal pushing increases, delivery of the newborn
3: delivery of the placenta, attachments separate and the placenta is delivered through mild contractions -may be eaten by the mother
If the animal is delivering many young, what does this mean with delivery of the fetus’ and placentas
Delivery of each will alternate
What is dystocia
How do you treat it
A problem in the delivery of a fetus due to size or position
Manual repositioning, c-sections, or fetotomy
What are some of the several changes that must occur in the fetus at birth
Lungs must start breathing air
Urachus must close to prevent urine leakage from umbilicus
Cardiovascular system must start delivering blood to the lungs and not the placenta
How does the cardiovascular system start delivering blood to the lungs and not the placenta after birth
Foramen ovale: a fetal opening between the right and left atria that shunts blood away from the lungs -closes after birth
Ductus arteriosus: connects the fetal aorta to the pulmonary trunk and shunts blood away from the lungs -shrinks and becomes a ligament after birth (helped by first breath by expanding the lungs and making it easier for blood to flow)
Ductus venosus: in the fetus it takes oxygenated blood from the umbilical vein to the caudal vena cava for circulation in the fetus -constricts and becomes a ligament after birth
What happens with time to the uterus after parturition (involution)
Involution: the gradual return of the uterus to its non-pregnant size (shrinks)
Sloughing of placental attachments
Myometrial contractions prevent continued bleeding and expel sloughed material and blood.
Discharge can be seen for a week or more after delivery and will gradually get darker
What are mammary glands and what do they do. Who are they in?
Specialized skin glands that produce colostrum and milk. Found in both males and females but only develops normally in females as secondary sex characteristics.
Grow during pregnancy and attain full size and function during first lactation
After weaning, milk production stops and gland regresses
In older animals the mammary glands regress and the tissue is replaced with connective tissue
Consists of the teat and mammae
What are mammae
The parenchyma (epithelial tissue) of the mammary gland, resembles lung tissue due to alveoli
Alveoli: milk secreting cells: alveoli connected to alveolar ducts join to form larger ducts which empty into a milk sinus
Milk sinuses: 2: where milk accumulates
Gland sinus: within the mammae
Teat sinus: within the teat
What is the teat (papillae)
Projected part of the mammary gland that contains the teat sinus. Has a streak canal which is a passage way leading from the teat sinus to the exterior teat opening
Describe the streak canal
A sphincter of muscle around the streak canal at the end of the teat prevents milk flow unless there is sucking/milking
Ruminants: one streak canal per teat
Equine: 2 streak canals per teat
Cats: several
Dogs: many
Why can only large animals be treated with intramammary meds
Too many openings that are too small in small animals
What are hard milkers? What are easy milkers?
Hard milkers: cows that have very tight sphincters (may be from fibrosis of streak canal)
Easy milkers: cows that leak milk have a loose sphincter (may be from frostbite and could be a route of infection)
What are the hormones that occur at puberty that stimulate mammary gland development
Prolactin: stimulate milk production
Growth hormone: development of udder
Estrogen And Progesterone: indirectly affect mammary gland development because they are produced in response to pregnancy/ovulation
Thyroid hormone and Corticosteroid hormones: could inhibit development if levels are too high
What is lactation and what hormones does it require?
Process of milk production
Requires: prolactin, growth hormone, and adrenal cortical hormones
When can males develop the ability to lactate
If Given hormones or with Sertoli cell tumors
What is milk composed of
Lipids (triglycerides)
Carbohydrates (lactose)
Proteins (caseins, lactalbumin, lactoglobulins)
Water
True or false
Animals who nurse frequently have a lower fat content in their milk
FALSE
it is higher
What is colostrum
The first milk after parturition
Contains large amounts of essential nutrients for newborns including; more proteins, lipids and amino acids, essential vitamins, laxatives, and antibodies/immunoglobulins (for immunity)
Why is there a laxative in colostrum
To help newborn clear the meconium (first feces after birth which is mainly soughed debris)
Why should colostrum be given to the newborn within minutes to 24 hours after birth?
To ensure passive immunity is passed onto the newborn because the newborns GIT becomes impermeable to immunoglobulin absorption and immunity will not be passed on (at first the GIT can only absorb intact proteins)
How is lactation maintained
Continues as long as nursing/Milking continues (as long as the gland is emptied and oxytocin release and hormones continue)
What is milk let down
Milk is stored high up in the mammary gland, needs appropriate stimulus to be “let down” into the teat sinus, stimulation is the physical act of nursing which releases oxytocin from posterior pituitary
Oxytocin causes contraction of the cells around the storage area of the gland and forces milk into the sinuses
Takes a few seconds to minutes
When is the term udder used
All mammae of ruminants and horses and sometimes sows
What does it mean to have supernumerary teats
More teats than usual which may or may not be connected to mammary tissue
Describe the mammary gland differences in a cow
Consists of 4 quarters, each with its own mammary gland
Intermammary groove separates the 2 halves of the udder (cranial and caudal quarters)
Milk vein: caudal superficial epigastric vein that runs along the ventral abdomen that drains the udder (don’t use for venipuncture or you risk damage)
Suspensory ligaments hold up the udder (can weigh >50 kg). These can break and give a dropped udder and splayed teats
Describe the canine mammary gland differences
Usually have 5 pairs (10 teats) but varies with breed (less in smaller breeds)
Maybe also vary on each side
Divided into throacic (2 pairs), abdominal (2 pairs) and inguinal (1 pair)
Describe the mammary gland differences in felines
Usually 4 or 5 pairs but can vary
Thoracic, abdominal and sometimes inguinal divisions
Describe the mammary gland differences in equine
1 pair, one teat on each side of the udder. Each teat has 2 streak canals and 2 teat cisterns (separate milk sinuses so they look like a cow udder internally)
Udder and teat are also covered with numerous sebaceous glands and sweat glands
What is mastitis
Inflammation of the mammary gland, usually associated with infection, can start in one teat and spread to others
Treatment: stripping the teats/sinuses completely, infusion of medications through the streak canals (have to strip out as well)
Signs: swelling, warm teat, redness, reduced milk production, painful on palpation
Cows: each quarter is separate so it can be in one or all four quarters
Describe tumors if the mammary glands, who is most affected and how are they treated?
Canines most frequently affected
Lumpectomy: removal of the tumor only
Mastectomy: whole gland removal
Ovariohysterectomy: to remove hormones on which tumors cells may depend on
Describe the variations of the female reproductive system in the canine
Ovaries: almond shaped, lie caudal to the kidneys, suspensory ligament of the ovary attaches the ovary to the last rib
Uterus: very long horns (adaptation for litter bearing), simple cervix with a cranioventral vaginal recess (fornix)
Vagina: vestibular bulbs (erectile venous plexus in vestibular walls, partly responsible for the tie during copulation) , os clitoris (small bone in some bitches)
Vaginal process: e vagina took of the parietal and visceral peritoneum through the inguinal canal that contains the round ligament
What are vaginal smears used for in small animals
To Evaluate the stage of estrus cycle for breeding purposes
Describe the variations of the female reproductive system in equines
Ovaries: bean shaped with well developed hilus, lie caudal to kidneys
Uterus: relatively short horns equivalent to length of uterine body
Cervix: simple cervix bulging into vagina with vaginal recess (fornix)
Describe the variations of the female reproductive system in bovine
Ovaries: almond shaped, lie at the pelvic inlet
Uterus: long horns, short bodies, ends of the horns are coiled up and are bound together by the intercornual ligament (gives false impression of being long), has mushroom like projections (caruncles)
long cervix with transverse folds (occlude canal with mucus secretions making it difficult to inject anything into uterus)
Vagina: distinct craniodorsal vaginal recess around the cervix (fornix)
Broad ligament: attached along the pelvic inlet instead of the dorsolateral body wall
What is dystocia and how is it treated
Difficulty giving birth due to size or position
Treatment: manual manipulation, traction, lubrication, fetotomy
What are the ovaries susceptible to
Several disease and abnormalities; hypoplasia, cystic follicles, neoplasia or can be congenitally absent or can descend through inguinal canal
Describe tubal ligation
Performed in people but not in animals
Sterilizes but does not stop estrus and unwanted behaviours
Describe ovariectomy/oophorectomy
Removal of the ovaries alone (newer procedure used in animals)
No increased risk of Pyometra
Similar in pain and time to ovariohysterectomy
Describe an ovariohysterectomy
Describe the procedure
Removal of the ovaries and uterus
Renders animal sterile and stops estrus
Most common elective surgery in carnivores
Procedure:
Suspensory ligament of the ovary is cut
Ligatures placed in ovarian vessels and broad ligament
Round ligament is broken down by blunt dissection (tearing) for faster clotting
The uterine stump is clamped, ligated and severed including the vessels
What does pregnancy or estrus do to surgery/spaying
Complicates the procedure by increasing blood supply
What is pyometra
Common in older unspayed dogs
Infection of the uterus (requires right hormonal conditions)
Prolonged luteal phase in dogs due to CL persisting (8-10 weeks) allows the cervix to remain open allowing bacteria to enter
After, progesterone thickens walls and increases secretions and the cervix closes, creating a perfect culture medium for bacteria
Treatment: medical treatment, ovariohysterectomy
Can use PGF2-alpha to save uterus (cause luteolysis to relax cervix and stimulate contractions)
What is endometritis
Infection or inflammation of the lining of the uterus
Common in horses and cattle
What is uterine adenocarcinoma
Malignant tumour of the uterus
Common in 3yo+ unspayed rabbits
Who is most susceptible to uterine prolapses
Postpartum cows and usually have milk fever
Who is most susceptible to vaginal prolapse
Postpartum cows due to prepartum straining
What is pneumovagina (wind suckers)
Most common in equine (conformational defect)
Sunken vagina, lips don’t close properly and they get contaminated when feces falls in or urine pools in the vestibule (creates a reproduction problem)
