Reproduction Flashcards
What are the four main factors of reproduction?
- gamete production: production of egg and sperm
- gamete maturation: ability of the gametes to be functional
- embryo development: after fertilization, growth of the embryo
- delivery of the young animal: parturition
Where are the testicles located and where do they migrate?
The testicles descend through the inguinal canal to the scrotum around the time of birth.
an exception includes chickens and other birds, as their testes remain inside of their bodies
What types of tissue are in the testicles?
interstitial tissue and seminiferous tubules
Describe interstitial tissue
within these tissues, cells of leydig produce testosterone which gives male characteristics (ex. antlers on deer, crested neck of a bull)
Interstitial tissue is found between the seminiferous tubules
Describe the seminiferous tubules
this is the site where spermatogenesis (sperm formation) occurs
these tubes are very long when uncoiled, stretching from a half a mile to a mile if they come from a bull
What are the functions of the scrotum?
- house and protect the testicles
- regulate temperature of the testicles (usually 3-13 degrees F lower than body temperature)
What is cryptorchidism and what types are there?
Cryptorchidism is a condition in which one or both of the testes fail to descend from the abdomen into the scrotum.
Unilateral or bilateral cryptorchidism can occur.
It can be genetically transmitted.
Describe unilateral cryptorchidism
one testicle does not descend through the inguinal canal
this somewhat reduces fertility
Describe bilateral cryptorchidism
neither testicle descends from the inguinal canal
This causes a definite reduction of testosterone levels and results in much lower fertility.
What is BSE in relation to reproduction?
BSE is a breeding soundness exam, where an animal’s reproductive capabilities and potential are examined.
Cryptorchid animals are not used to breed since the condition can be passed on genetically.
Describe the structure of the epididymis
There is a head at the top of the testicle, a body, and a tail at the bottom of the testicle
What are the functions of the epididymis?
- storage of sperm cells
- provision of maturation space for sperm cells
- nutrition of sperm cells through secreted substances
What is the anatomical relationship of the epididymis to the testicles?
The head of the epididymis connects the seminiferous tubules through efferent ductules
What is the Vas deferens?
The Vas deferens is a structure that carries sperm cells and substances from the epididymis to the urethra.
Some species, like bulls, have an enlarged portion of the vas deferens called the ampulla, which is located near the end of the vas deferens.
Describe some of the accessory sex glands and their functions
Accessory sex glands contribute to reproduction, but sperm do not travel through them. Size of these glands varies by species.
- seminal vesicle: (vesicular gland) two of them
- prostate: one
- bulbo-urethral (Cowper’s): two
What are the functions of the accessory sex glands?
- secrete nutrients
- secrete buffers
- secrete substances to cleanse and lubricate urethra
- volume of semen produced depends of the size of the glands (ex. boars have large accessory glands and therefore ejaculate larger amounts of semen)
What are the functions of the penis and urethra?
The penis is the organ of copulation for males.
The urethra is a large canal in the penis that semen passes through during ejaculation.
What is sigmoid flexure?
This is a retractable, muscle controlled presentation of the penis seen in pigs, sheep, cattle, and goats. There is a “S” shaped movement.
Describe the composition of semen.
- Spermatozoa
- Secretions - quantities and concentrations varies by species
accessory glands
vas deferens
epididymis
What is the relationship between sperm concentration and volume of semen ejaculation?
Higher volumes of semen have lower concentrations of sperm per mL of ejaculatory fluids.
How does the male reproductive system in avian species differ from that of mammals?
There is variation in specific structures like the testicles, epididymis, and vas deferens. There is also variation in semen.
How do the testicles of avian species compare to those of mammals?
The testicles are the same as mammals, but are located inside of the body.
How does the epididymis of avian species compare the structure in mammals?
The epididymis is birds is the same as in mammals, but it is located inside of the body.
How does the vas deferens in avian species compare to this structure in mammals?
The vas deferens conducts semen into the cloaca instead of a urethra.
How does semen from avian species compare to semen from mammals?
Semen in avian species is more concentrated and has a lower volume than ejaculations from mammals. This is because birds lack accessory sex glands, so less is contributed to the seminal fluid.
Where are the ovaries located?
just behind the kidneys
What are the functions of the ovaries?
- Oogenesis: production of eggs
- Hormone production
What are the hormones produced by the ovaries and what are their functions?
- Estrogen: from growing (graafian) follicles, produces most of the female characteristics
- Progesterone: from corpus luteum; formed after ovulation when the follicle collapses, helps maintain pregnancy
- Relaxin: loosens pelvic area during parturition
What is the oviduct and what are the functions?
The oviduct is also known as the fallopian tube.
- After ovulation, the egg is caught by the infundibulum (catcher’s mitt) at the part closest to the ovary
- fertilization occurs in the oviduct, and the zygote is then transported to the uterus
Describe the structure of the uterus.
The uterus has a body and two horns.
The uterine lining is largely muscle.
Longer uterine horns are characteristic of animals that give birth to litters.
What are the functions of the uterus?
- Sperm movement
- nourishment via uterine milk
- attachment and nourishment of fetus via placenta
- contractions force fully developed fetus outside (parturition)
What is the cervix and what are its functions?
The cervix is the lower outlet of the uterus, and it is made up of connective tissue.
Functions:
1. changes along with stages of estrous and pregnancy
2. open when the animal is in heat (wants to mate) and closed (plug) during pregnancy to prevent invasion of bacteria, etc.
The mucous layers help regulate the cervix. Animals in heat have a thinner mucous layer, while pregnant animals have a thick cervical mucous layer.
What is the function of the vagina?
Female organ of copulation and birth canal
What is the purpose of the vulva?
It is the external opening to the female reproductive system
Where are the ovaries of a female avian species, and what are the functions?
The ovaries are close to the kidneys.
Function:
Only the left ovary functions, and it has many follicles in different stages that are present at the same time.
What are the components of the oviduct in avian species?
- Infundibulum (3 in)
- Magnum (15 in)
- Isthmus (4 in)
What are the functions of the infundibulum in avian species?
It receives yolk, secretes chalaziferous layer and vitelline membrane
What is the function of the magnum in avian species?
secretes most of the albumen layers
What is the function of the isthmus in avian species?
secretes inner and outer shell membranes
What is the shell gland and what does it do?
The shell gland is the uterus, and it secretes the shell in about 12 hours (varies by bird)
What is the difference between the vagina in avian species and mammals?
The vagina secretes substances that act as the cuticle.
It also contains crypts to catch sperm and stores them.
How long does egg formation take?
25-26 hours
Why does sperm in the avian reproductive system live longer in the female reproductive tract?
It lives longer because the sperm is similar in temperature to the female reproductive system.
What is mitosis?
Asexual division of body cells where the number of chromosomes stays constant (diploid)
What is meiosis?
Occurs in the seminiferous tubules or ovaries, and the resulting cells are haploid. (gametogensis)
Describe spermatogenesis
Spermatogenesis is constant after the onset of puberty, and billions of sperm are produced
Describe oogenesis
The number of eggs is set before birth, and it is cyclic after the onset of puberty. Conservation of cytoplasm in an important factor because the majority of the cytoplasm is directed to one large cell, the egg.
Describe copulation
In most species, the females permit copulation during receptive periods (estrus).
Visual cues to males include tail wagging, elevated tails, etc.
Pheromones are volatile chemical products that can trigger mating behaviors in animals of the same species. They are usually scents or smells released into the air.
How many sperm are produced by a primary spermatocyte?
4 sperm produced from each
How many sperm are produced by secondary spermatocytes?
2 sperm formed from each
How many egg cells are produced by a primary oocyte?
1 functional egg is produced.
What else is formed during oogenesis besides the egg?
polar bodies