Reproduction Flashcards
(132 cards)
1
Q
What are the four main factors of reproduction?
A
- 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
2
Q
Where are the testicles located and where do they migrate?
A
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
3
Q
What types of tissue are in the testicles?
A
interstitial tissue and seminiferous tubules
4
Q
Describe interstitial tissue
A
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
5
Q
Describe the seminiferous tubules
A
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
6
Q
What are the functions of the scrotum?
A
- house and protect the testicles
- regulate temperature of the testicles (usually 3-13 degrees F lower than body temperature)
7
Q
What is cryptorchidism and what types are there?
A
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.
8
Q
Describe unilateral cryptorchidism
A
one testicle does not descend through the inguinal canal
this somewhat reduces fertility
9
Q
Describe bilateral cryptorchidism
A
neither testicle descends from the inguinal canal
This causes a definite reduction of testosterone levels and results in much lower fertility.
10
Q
What is BSE in relation to reproduction?
A
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.
11
Q
Describe the structure of the epididymis
A
There is a head at the top of the testicle, a body, and a tail at the bottom of the testicle
12
Q
What are the functions of the epididymis?
A
- storage of sperm cells
- provision of maturation space for sperm cells
- nutrition of sperm cells through secreted substances
13
Q
What is the anatomical relationship of the epididymis to the testicles?
A
The head of the epididymis connects the seminiferous tubules through efferent ductules
14
Q
What is the Vas deferens?
A
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.
15
Q
Describe some of the accessory sex glands and their functions
A
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
16
Q
What are the functions of the accessory sex glands?
A
- 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)
17
Q
What are the functions of the penis and urethra?
A
The penis is the organ of copulation for males.
The urethra is a large canal in the penis that semen passes through during ejaculation.
18
Q
What is sigmoid flexure?
A
This is a retractable, muscle controlled presentation of the penis seen in pigs, sheep, cattle, and goats. There is a “S” shaped movement.
19
Q
Describe the composition of semen.
A
- Spermatozoa
- Secretions - quantities and concentrations varies by species
accessory glands
vas deferens
epididymis
20
Q
What is the relationship between sperm concentration and volume of semen ejaculation?
A
Higher volumes of semen have lower concentrations of sperm per mL of ejaculatory fluids.
21
Q
How does the male reproductive system in avian species differ from that of mammals?
A
There is variation in specific structures like the testicles, epididymis, and vas deferens. There is also variation in semen.
21
Q
How do the testicles of avian species compare to those of mammals?
A
The testicles are the same as mammals, but are located inside of the body.
22
Q
How does the epididymis of avian species compare the structure in mammals?
A
The epididymis is birds is the same as in mammals, but it is located inside of the body.
23
Q
How does the vas deferens in avian species compare to this structure in mammals?
A
The vas deferens conducts semen into the cloaca instead of a urethra.
24
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.
25
Where are the ovaries located?
just behind the kidneys
26
What are the functions of the ovaries?
1. Oogenesis: production of eggs
2. Hormone production
27
What are the hormones produced by the ovaries and what are their functions?
1. Estrogen: from growing (graafian) follicles, produces most of the female characteristics
2. Progesterone: from corpus luteum; formed after ovulation when the follicle collapses, helps maintain pregnancy
3. Relaxin: loosens pelvic area during parturition
28
What is the oviduct and what are the functions?
The oviduct is also known as the fallopian tube.
1. After ovulation, the egg is caught by the infundibulum (catcher's mitt) at the part closest to the ovary
2. fertilization occurs in the oviduct, and the zygote is then transported to the uterus
29
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.
30
What are the functions of the uterus?
1. Sperm movement
2. nourishment via uterine milk
3. attachment and nourishment of fetus via placenta
4. contractions force fully developed fetus outside (parturition)
31
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.
32
What is the function of the vagina?
Female organ of copulation and birth canal
33
What is the purpose of the vulva?
It is the external opening to the female reproductive system
34
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.
35
What are the components of the oviduct in avian species?
1. Infundibulum (3 in)
2. Magnum (15 in)
3. Isthmus (4 in)
36
What are the functions of the infundibulum in avian species?
It receives yolk, secretes chalaziferous layer and vitelline membrane
37
What is the function of the magnum in avian species?
secretes most of the albumen layers
38
What is the function of the isthmus in avian species?
secretes inner and outer shell membranes
39
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)
40
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.
41
How long does egg formation take?
25-26 hours
42
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.
43
What is mitosis?
Asexual division of body cells where the number of chromosomes stays constant (diploid)
44
What is meiosis?
Occurs in the seminiferous tubules or ovaries, and the resulting cells are haploid. (gametogensis)
45
Describe spermatogenesis
Spermatogenesis is constant after the onset of puberty, and billions of sperm are produced
46
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.
47
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.
48
How many sperm are produced by a primary spermatocyte?
4 sperm produced from each
49
How many sperm are produced by secondary spermatocytes?
2 sperm formed from each
50
How many egg cells are produced by a primary oocyte?
1 functional egg is produced.
51
What else is formed during oogenesis besides the egg?
polar bodies
52
Describe where semen deposition occurs in common species.
Uterus in swine or horses
Vagina in most animals, including cattle, sheep, and goats
Cloaca-vagina in birds: females assume a mating crouch and the cloacas make contact to deposit the sperm. Male birds tend to not have a well developed copulatory organ
53
Describe sperm storage
In most species, sperm has a short lifespan. The exception is birds, as they can store sperm in their vaginal crypts.
54
Describe sperm transport
From the vagina to the uterus, sperm travel by their own motility using their tails.
From the uterus to the oviduct, sperm use their own motility, but are also aided by muscular contractions by the female.
55
Describe capacitation and fertilization
Sperm must develop the capacity to fertilize mature eggs.
Capacitation is when the acrosome (head) of the sperm undergoes changes and it able to penetrate the egg's outer coating (zona pellucida). The purpose of this is to make sure only one sperm penetrates the egg.
As soon as fertilization occurs, the fertilized egg becomes known as a zygote, and it gets nourishment from the egg's cytoplasm.
56
Describe prenatal development
Within the oviduct, the zygote divides and travels toward the uterus.
It receives nourishment from the egg's cytoplasm, is free floating, and rapidly divides.
Within the uterus, the blastocyst develops.
Formation of extra-embryonic membranes.
57
What is the blastocyst?
blastocyst: zygote that has been dividing as it goes down the oviduct and enters the uterus
58
What are the extra-embryonic membranes?
yolk sac
amnion
chorion
allantois
allantochorion
59
What is the yolk sac?
an extra-embryonic membrane that provides early nutrients (uterine milk) and degenerates after a few days
60
What is the amnion?
the sac that surrounds the fetus, and is filled with fluid
it protects the fetus and absorbs shock
it does not fuse with anything
61
What is the chorion?
a layer that surrounds the amnion sac
62
What is the allantois?
The allantois is the structure that takes on the role of nutrient absorption after the yolk sac degenerates
63
What is the allantochorion?
The allantois and the chorion membranes fuse together and attach to the uterine lining.
64
What is implantation?
occurs when the allantochorion attaches to the uterus
one of the leading causes of infertility is inability to implant
implantation does not occur until about 1/3 of the way though pregnancy
heat stress is a major cause of implantation failure
65
What is the placenta?
The exchange organ between the mother and fetus that allows for the exchange of nutrients and waste. There is no direct blood exchange.
The types of placentae are diffuse and cotyledonary
66
Describe a diffuse placenta
The entire surface of the allantochorion attaches to the uterus. This type is present in horses
67
Describe the cotyledonary placenta
The attachment of the allantochorion takes place in specialized areas. Curuncles from the uterine wall fuse with cotyledons from the placenta to form placentomes.
This type of placenta is present in ruminants.
68
What are the sources of nutrients for the fetus during prenatal stages?
Before implantation: uterine milk in yolk sac or the allantois
After implantation: mother's blood supply, as nutrients are exchanged through the placenta (no direct blood exchange)
69
Define gestation
the period from conception until parturition
70
Describe the hormones involved with parturition
Prenatal development is terminated by parturition.
1. Initiation - cortisol from fetal adrenal cortex; hormone levels change and uterus contracts
2. Relaxin: from ovary, helps relax cartilage and ligaments in pelvis
3. Oxytocin from posterior pituitary causes uterine contractons
4. Membranes - placenta vs. afterbirth
71
What are the differences in prenatal development in female avian species?
During incubation, formation of the extraembryonic membranes occurs (yolk sac, amnion, allantois, chorion)
The length of incubation varies by species and temperatures. Chickens have an incubation period of 20-21 days while it is 28 days in turkeys. High humidity and a temp of 100 degrees F is ideal.
Unlike mammals, the allantois and chorion do not fuse in an egg, and most nutrients come from the yolk sac.
Prenatal development is terminated by hatching. Vasotocin is a hormone that functions like oxytocin during egg laying. Chicks can use their egg tooth to break out of a shell, and the egg can sustain life up to three days after hatching due to the shell membranes.
72
What is the function of follicle stimulating hormone in male mammals?
FSH stimulates spermatogenesis in the seminiferous tubules
73
What is the function of luteinizing hormone in male mammals?
LH stimulates the production of testosterone in the interstitial tissue.
74
What controls the release of the gonadotropins FSH and LH?
GnRH - gonadotropin releasing hormone - from the hypothalamus stimulates the anterior pituitary to secrete FSH and LH
75
How is the release of hormones in avian species different than in mammalian species?
Birds are receptive to a photoperiod, where the length and light exposure helps control hormone release. The length of the photoperiod determines when the anterior pituitary releases the gonadotropins.
76
What is the function of follicle stimulating hormone in female mammals?
stimulates development of graafian follicles and estrogen production (secreted by AP)
77
What is the function of luteinizing hormone in female mammals?
Triggers ovulation and stimulates growth and development of the corpus luteum (secreted by AP)
78
What is the function of estrogen?
Estrogen is secreted by the graafian follicles in the ovaries, and it causes sexual excitability and development of female characterisitics
79
What is the function of progesterone?
Progesterone is secreted by the corpus luteum in the ovaries, and it maintains pregnancy
80
What is the estrous cycle?
This is the period between ovulations.
It lasts 21 days in cows, sows, and mares. It lasts 16 days in ewes.
The phases are: proestrus, estrus, metestrus, diestrus
81
Describe the proestrus phase
follicles are developing on the ovary; estrogen levels are increasing
82
Describe the estrus phase
The estrus phase is what we call "heat"; female is receptive to the male; high estrogen levels and surge of LH; release of ovum
83
Describe the metestrus phase
corpus luteum is forming and begins to produce progesterone
84
Describe the diestrus phase
functioning corpus luteum produces a lot of progesterone
85
What happens if pregnancy occurs during the estrous cycle?
Corpus luteum is maintained and further estrus(heat) is inhibited
86
What happens if no conception occurs during the estrous cycle?
Prostaglandin from the uterus causes regression of the corpus luteum (known as the corpus albicans), and proestrus begins
87
How does progesterone act as a negative feedback mechanism?
High levels of progesterone feed back to the hypothalamus and inhibits the release of GnRH, preventing the animal from going back into heat if they are pregnant.
88
Role of follicle stimulating hormone?
stimulates sperm and follicle development
89
Role of estrogen?
brings animal into heat
90
Role of LH?
stimulates ovulation and development of the corpus luteum; testosterone production
91
Role of progesterone?
maintains pregnancy
92
What are some additional functions of estrogen?
1. development of female reproductive system
2. causes tissue lining the uterus to thicken and increase blood supply
3. production of thin mucous in the cervix
4. makes uterus sensitive to oxytocin
5. makes uterus more resistant to infection
93
What are some additional functions of progesterone?
1. increases growth and blood supply to lining of uterus
2. secretion of uterine milk
3. prevent muscle contractions of uterus
4. production of thick mucous by cervix
94
What is the function of prostaglandin?
Prostaglandin is a hormone produced by the uterus, and it targets the corpus luteum to become non-functional if fertilization does not occur.
95
What is the role of follicle stimulating hormone in female avian species?
associated with follicular growth - fairly constant
96
What is the role of luteinizing hormone in female avian species?
causes ovulation - cyclic - partially stimulated by light intensity and length (photoperiod)
97
How are eggs released?
Eggs follow a hierarchical order, that is, they are released in order of size.
98
How do neurohormonal signals play a role in avian reproduction?
1. First, the egg is in the clutch (or after an egg leaves the magnum): nerves signal a hormonal response so an egg is sent to the magnum
2. While the egg is in the magnum: nerve signals prevent another egg from going to the magnum
99
Discuss egg abnormalities
Double yolks: 2 eggs released at the same time or one yolk is lost and then "found" the next day
Soft shelled eggs: egg is laid prematurely and shell is not fully formed (usually caused by the bird itself)
Thin shelled eggs: dietary deficiency
100
What does it mean to be a continuous breeder?
Continuous breeders have no distinct mating season and are polyestrous.
Cows and sows are examples of continuous breeders.
101
What does it mean to be a seasonal breeder?
The animal will only mate at certain times of the year. These females only have their estrous cycles during certain times.
Examples are sheep, mares, and birds.
102
What is the difference between sterility and sub-fertility?
Sterile animals cannot reproduce while sub-fertile animals may reproduce, but not at an optimal rate.
103
What are some causes of sterility and sub-fertility?
Anatomical defects like cryptorchidism can be a cause.
Freemartins are sterile females born twin to a male.
Endocrine malfunctions can also be a cause.
Cystic ovaries can occur, preventing the follicle from rupturing, leaving the animal in constant estrus (heat).
A persistent corpus luteum that will not regress can also prevent the animal from entering estrus.
104
How can reproductive efficiency be measured?
1. conception rate
(# pregnancies/ # of breedings)
2. number of live births
3. pregnancy rate (heat detection rate x conception rate)
105
What major factors influence fertility?
1. failure to mate to fertile male
2. fertilization failure
3. early embryonic death
4. fetal death - rare, except for disease
5. nutrition, disease, etc.
106
Why is artificial insemination (AI) used?
1. breeds more females
2. more genetic progress
3. more economical
4. safety
5. disease control
107
What animals are commonly bred via AI?
90% turkey broilers
70% dairy cows
< 10% beef cows
108
Why are horses rarely bred via AI?
Some horses, especially racehorses, would have their value decrease if their sperm was sold for AI.
109
How is semen collected for AI?
Artificial vaginas can be used for bulls, stallions, rams, goats etc.
The male will mount the female or another object and the artificial vagina will collect the ejaculate.
Other methods are also available.
110
What is electroejaculation?
This is when a low grade electric current is ran through the accessory sex glands of the male, causing ejaculation. This method is typically used as a last resort, and is used on older males that may have trouble mounting for other methods of semen collection.
111
How is semen handled immediately after it's acquired and what risks are involved?
The semen could experience temperature shock if the temp is too high or too low.
It must avoid contamination and be placed in some clean equipment appropriate for its volume.
Concentration, motility, and structure can be measured.
112
Why is sperm diluted when it is collected for AI, and what diluents are used?
Sperm is diluted to increase its volume and prolong the lifespan of it.
Some diluents used are egg yolk citrate or tris buffers. Milk and glycerol can also be utilized. The glycerol is added to prevent to formation of ice crystals during storage because milk has a lower phospholipid count than glycerol.
The diluent usually has a nutrient source and a buffer to control the pH so the sperm don't die.
113
How is semen collected for AI stored?
Storage vessels like straws are common.
Some semen is frozen in liquid nitrogen for longer term storage.
Fresh semen can also be maintained around 40 degrees F.
114
How is the semen utilized for conception in AI and what must be considered?
The duration of estrus and ovulation are variable. Some times during the cycle have a higher chance of conception.
For instance, in cattle, estrus lasts around 12-18 hours, with ovulation occurring 12 hours after the end of estrus. The best time to inseminate the cow is mid-estrus to end of estrus, as their is an 86% conception rate during this window.
115
How is the semen deposited during AI depending on the animal?
In cattle, the insemination tube is passed through the cervix and semen is deposited in the uterine body.
For goats or sheep, the semen is deposited in the uterus or cervix.
In mares, the semen is deposited in the uterus or the last part of the cervix.
In turkey, it is deposited in the oviduct because only the left one is functional, and we want to ensure that fertilization has the best chances to occur.
116
How is estrus detected among certain animals?
In cattle, they should be checked daily. They display "standing heat," restlessness, or clear discharge.
In swine, they take on a rigid stance, and have a red, swollen vulva.
Mares will frequently urinate, or have contractions of the vulva (winking).
117
What factors influence conception rate?
1. semen quality
2. receptivity of female
3. ability of inseminator
4. nutritional plane, disease, status, stress level of female
118
What is estrus synchronization?
Controlling the estrous cycle so that a herd or flock of females come intro estrus (heat) at approximately the same time.
advantages:
1. reduces labor for heat detection
2. helpful in embryo transfer programs
119
How can estrus synchronization be accomplished?
The females can be injected with prostaglandin, which destroys the corpus luteum and brings the animal back into estrus after some time.
120
How does embryo transfer occur?
An egg is removed from a mother's (donor) reproductive tract and transferred to another female's (recipient) tract.
The embryo may be fresh or frozen.
The purpose of embryo transfer is to increase the number of offspring from outstanding females.
121
What other actions are performed for the donor animal during embryo transfer?
The donor is superovulated, receiving hormone injections like FSH to increase egg production.
The female is bred with two doses of semen, and fertilized eggs are recovered by flushing the uterus with a buffered solution.
122
What is the difference between fresh and frozen embryos?
Fresh embryos have a higher conception rate than frozen ones.
Frozen embryos are easier to ship and transport, and can be stored to react to market conditions.
123
What is in-vitro fertilization and what are some of the advantages that accompany it?
IVF is a biotechnology procedure where immature oocytes can be harvested, mature, and then be mated with sperm outside of the body.
Advantages:
1. Oocytes easily obtained from high value animals, both living and recently deceased
2. a good alternative to superovulation - embryos can be collected almost anytime
124
How is semen sexed?
A centrifuge is used to separate the sperm cells, but this is not the preferred method.
Dyes and lasers can be used to separate semen based on the weight of their chromosomes.
125
What are the four stages of the reproductive life cycle?
1. before puberty
2. puberal
3. adult
4. senescent
126
Describe the prepuberal stage
Primary follicles have been formed (number set before birth); basis for adult behavior may be forming
127
Describe the puberal stage
Endocrine changes; reproductive competence acquired
Influenced by age and weight
128
Describe the adult stage
Capacity to produce and release gametes for extended periods
Females: available follicles decreased by atresia (shrinkage of follicles)
129
Describe the senescent stage
Reproductive capacity decreases due to direct and indirect effects (deterioration of the reproductive tract or poor nutrition, etc.)
130
What are some critical nutrients in reproduction?
protein: sperm, ova, epithelial lining of reproductive tracts
Vitamin A: helps maintain epithelial linings (too low - linings harden, inhibiting fluid and sperm/ova movements)
Vitamin E: helps maintain fertility
Calcium: needed in birds for shell formation
Positive energy levels are needed - low energy levels may cause females to not have estrous cycle or to not conceive
131
What are some effects of good reproductive practices in production fields?
1. more total offspring
2. more females conceive in specific time periods
3. less feed, labor, and breeding costs
4. lower cull rate
5. more total production
