Chapter 19 Reproductive System

Question 1

Why Sex?

Answer 1

 Survival of the species
*All other body systems are about the survival of the individual animal
 Economic system for agricultural species
* Dairy
*Beef
*Equine (horse racing)
*Pork

Question 2

Asexual vs. Sexual Reproduction

Answer 2

 Asexual reproduction – massive numbers of
“offspring” in short period of time, all organisms with same DNA
*Bacteria, protozoans, cloning
 Sexual reproduction – fewer numbers of offspring, all organisms with different DNA
*Increased genetic diversity (larger gene pool)
*Increased survival of the species
* Most multicellular organisms

Question 3

Animal Reproductive System Physiology

Answer 3

 Works to ensure survival of the species of the animal
 Interacts with other body systems
*Purely reproductive structures are not essential to the life of an animal
 Requires a second animal (of the opposite sex) tocfully carry out its function
 Process begins with fertilization
* Head of spermatozoon must penetratecinto the cytoplasm of ovum
— S + E= Z

Question 4

Chromosomes

Answer 4

 Coiled masses of DNA in the nuclei of cells
 Each cell in an animal’s body (except spermatozoa or ova) contains paired, identical chromosomes
 Diploid chromosome number = 2n
* Total number of chromosomes in the nucleus of each body cell is the same (except for reproductive cells)
* Always an even number – chromosomes occur in pairs.

Question 5

Sex Chromosomes

Answer 5

 Designated as either “X” chromosomes or “Y” chromosomes
 If both of the sex chromosomes are X chromosomes (XX), the individual is genetically female
 If one is an X and the other is a Y (XY), the individual is genetically male

Question 6

Mitosis vs. Meiosis

Answer 6

 Mitosis – diploid chromosome number (2n)
*Production of all cells in body except gametes
 Meiosis – haploid chromosome number (n)
*Production of gametes (sex cells)
 Fertilization
*Sperm (n) + ovum (n) = =
zygote (2n)

Question 7

Cell Division Mitosis vs Meiosis

Answer 7

 Mitosis = 2n
* Each chromosome produces a duplicate copy of itself
* Half of chromosomes go to one daughter cell, and half go to the other
* Genetic makeup exactly the same as each other and as the parent cell

 Meiosis = n
* Chromosomes do not produce duplicate copies before daughter cells pull apart
* Random half of total chromosomes go to each daughter cell

Question 8

Mitosis

Answer 8

 Most body cells divide after the cell first makes a duplicate copy of its chromosomes
 Half the chromosomes go to one daughter cell and half go to the other
 Genetic makeup of the two daughter cells is exactly the same as each other and as the parent cell

Question 9

Meiosis

Answer 9

 Cell division that produces basic reproductive cells
* Ova
*Spermatozoa
 Process ensures that the genetic makeup
of each new animal is unique
 Creation of reproductive cells (gametes)
*Sperm & egg
* Occurs in gonads (sex organs)
 Diploid (2n) number  haploid (n) number
 Meiosis I (where genetic diversity happens)
* Tetrads
* Crossing over
 Meiosis II
* Like mitosis

Question 10

Haploid Chromosome Number (meiosis)

Answer 10

 The reduced number of chromosomes in the gamete
 Results from a reduction division (meiosis)
* Cell divides
* Total number of chromosomes in each daughter cell is reduced to ½ number of the parent cell
 Ensures that fertilized ovum from union of ova and
spermatozoa has the diploid number

Question 11

Meiosis – Gamete Formation

Answer 11

 Diploid number to haploid number of chromosomes
 Spermatogenesis in male animal
* 1 spermatogonium produces 4 mature sperm
 Oogenesis in female animal
* 1 oogonium produces 1 mature egg (ovum) + 3 polar bodies

Question 12

Spermatogenesis

Answer 12

The process where spermatozoa (male gametes) are produced in large numbers in the seminiferous tubules of the testes
 Primary spermatocyte divides by meiosis into secondary spermatocytes – haploid number
 The secondary spermatocytes divide by mitosis into four spermatids
 Spermatids grow tails and undergo other physical changes that convert them to spermatozoa.
 When the spermatozoa are fully developed, they detach and are carried to the epididymis for storage before ejaculation
 Half of the spermatozoa produced have an “X” sex
chromosome, and half have a “Y” sex chromosome
*The male sperm determines the sex of the
offspring!

Question 13

Oogenesis

Answer 13

*The process where ova (female gametes) are produced (a few at a time) in the follicles of the ovaries
*Female has fixed number of primary oocytes at or soon after birth

 Primary oocyte divides by meiosis into a large secondary oocyte and a small “polar body”
 Each has the haploid chromosome number
 Secondary oocyte and the first polar body divide by mitosis into an ovum and three polar bodies

Question 14

The Male Reproductive System

Answer 14

*The testes are the male gonads
*The male reproductive cells are formed in the testes Testes located outside body in the scrotum

Question 15

Male Reproductive System Physiology

Answer 15

 Produces male sex hormones
 Develops spermatozoa
 Deliver the spermatozoa to the female system at the appropriate time

Question 16

Male Reproductive System Anatomy

Answer 16

 Scrotum
* Cremaster muscle
* Tunica albuginea
 Testicles (testes)
 Epididymis
 Spermatic cord
* Ductus deferens (vas deferens)
* Testicular vessels

Question 17

Scrotum

Answer 17

 Sac of skin that houses the testes
 Helps regulate temperature of testes
* Testes must be kept slightly cooler than body temperature
 Cremaster muscle passes down through the inguinal ring and attaches to the scrotum.
*Adjusts the position of the testes relative to the body depending on temperature

Question 18

Tunica Albuginea

Answer 18

 Fibrous connective tissue capsule that encloses each testis
 Septa divide each testis into tiny lobules that contain the seminiferous tubules
 Produce sperm and hormones
 Located outside the abdomen in the inguinal region
 Housed in a sac of skin – the scrotum

Question 19

Histology of Testicle

Answer 19

 Seminiferous tubules
*Produce sperm (spermatogenesis)
 Interstitial cells (Cells of Leydig)
*Produce testosterone

Question 20

Seminiferous Tubules

Answer 20

 Site of spermatogenesis
*takes place in U-shaped tube =
 Long, convoluted U-shaped tube attached at both ends to system of ducts (rete testis)
 Interstitial cells – endocrine cells between the seminiferous tubules -produce androgens
*produce androgens (testosterone)
 Sertoli cells – Support developing spermatids
*and shield from body’s immune system

Question 21

Testicle Development

Answer 21

 Develop just posterior to kidneys
 Descends into scrotum by passing through inguinal canal
 Gubernaculum (cordlike structure containing muscle) extends from the testicle to the inner lining of scrotum
*It shortens, and guides the testicle to the scrotum

Question 22

Functions of the Testes

Answer 22

 Spermatogenesis
*Spermatozoa are produced in seminiferous tubules of the testes
 Hormone production
*Androgens (male sex hormones) produced in interstitial cells of the seminiferous tubules
*Principal androgen = testosterone

Question 23

Spermatozoa

Answer 23

 Long, thin cells
 3 main parts
* Head - made up of nuclear material and is covered by a cap-like structure called the acrosome
– Acrosome contains digestive enzyme that are released once the sperm is inside the female reproductive tract – helps penetrate through the ovum)
* Midpiece - the “power plant” of the cell; contains a large
concentration of energy-producing mitochondria
* Tail - – resembles the flagellum that many single-celled organisms use for propulsion;

Question 24

Head of sperm

Answer 24

 Contains nucleus
 Covered by acrosome
* Contains digestive enzymes that help spermatozoon reach and penetrate ovum

Question 25

Midpiece of sperm

Answer 25

 Large concentration of mitochondria arranged in a spiral pattern

Question 26

Tail of sperm

Answer 26

 Contains muscle-like contractile fibrils * Produces a whip-like movement of tail and propel sperm cell forward

Question 27

Duct System

Answer 27

 After detaching from Sertoli cells, spermatozoa enter the rete testis  Then flow through the efferent ducts to the epididymis *Single, long, convoluted tube that connects the efferent ducts of the testis with the vas deferens *Storage and maturation of spermatozoa  Then flow into the vas deferens of the spermatic cord

Question 28

The Epididymis of sperm

Answer 28

 Storage site for spermatozoa and a place for them to mature  Flat ribbon-like structure that lies along the surface of the testis

Question 29

Vas Deferens

Answer 29

 Ductus deferens; part of the spermatic cord  Passes through inguinal ring then separates from spermatic cord and connects with urethra  Ampulla – enlargement of the vas deferens just before it joins the urethra found in some species * contain glands that contribute material to semen

Question 30

Spermatic Cord

Answer 30

 Blood and lymphatic vessels, nerves, and the vas deferens.  Pampiniform plexus – meshwork of veins that surrounds testicular artery * Maintains testes at a temperature slightly lower than body temperature * Warms blood back to body temperature before it returns to the abdomen.

Question 31

Vas Deferens Physiology

Answer 31

*moves the spermatozoa from the epididymis up to the urethra when ejaculation occurs *spermatozoa mixed with secretions from accessory glands = semen

Question 32

Urethra anatomy

Answer 32

 Pelvic portion - entry point of vas deferens and accessory reproductive glands  Penile portion - runs down the length of the penis  Spermatozoa from vas deferens and secretions from accessory reproductive glands enter urethra and are pumped out as semen  Carries urine from the urinary bladder outside the body. * Urine flow temporarily blocked when ejaculation occurs

Question 33

Accessory Reproductive Glands

Answer 33

*Ducts of glands enter pelvic portion of the urethra *Different species have different combinations of glands  Produce alkaline fluid to help counteract acidity of female reproductive tract *Electrolytes * Fructose *Prostaglandins  Seminal vesicles  Prostate gland  Bulbourethral glands = Cowper’s glands

Question 34

The Penis

Answer 34

 The roots * 2 bands of crura attach penis to brim of pelvis  The body * 2 bundles of erectile tissue *Sinuses engorge with blood = erection --Corpus cavernosum urethrae = corpus spongiosum --Corpus cavernosum penis

Question 35

The Penis Glans

Answer 35

 The glans * Distal end of penis with numerous sensory nerves *Prepuce = sheath of skin that encloses the penis when it is not erect

Question 36

Penis Comparative Anatomy

Answer 36

*Canine  Urethra runs through groove on os penis  Bulb of the glans remains swollen after ejaculation . . .the tie *Equine  Contains large component of erectile tissue  Glans flares into distinctive mushroom shape -- Corona glandis  Urethral process extends from central depression called the fossa glandis *Bovine  Sigmoid Flexure Erection results from straightening the S shape of non-erect penis  Penis protrudes from prepuce for breeding  Retractor penis muscle pull penis back to non-erect, S shape

Question 37

Orchidectomy

Answer 37

 Castration, “neutering”, OE  Definition – surgical removal of testicles  Medical vs. behavioral reasons

Question 38

Male Physiology

Answer 38

* Major sex hormone is testosterone * Produced in the interstitial cells in the testicle

Question 39

Female Reproductive System complexity and functions

Answer 39

 More complex than male reproductive system  Functions: *Produces sex hormones * Develops gametes * Receives male gametes * Furnishes a site for gametes to fertilize the ovum *Provides environment for embryo to grow and develop * Carries embryo for entire pregnancy *Pushes offspring out when fully developed

Question 40

Canine Female Reproductive System Anatomy

Answer 40

 Ligaments  Ovaries  Oviducts  Uterus  Cervix  Vagina  Vulva

Question 41

Broad and Round Female Reproductive Ligaments

Answer 41

 Broad ligament: *Suspend ovaries, oviducts, and uterus * Contain blood vessels and nerves  Round ligament of the uterus

Question 42

Suspensory Ligament of Ovary

Answer 42

 Ovarian end of broad ligament attached to body wall in area of last rib  Must be broken during OHE

Question 43

Ovaries

Answer 43

 In dorsal abdomen just posterior to kidneys  Species variation in appearance  Site of oogenesis  2 functions * Ova (eggs) * Female hormones -- Estrogen - prepares for pregnancy ---progesterone - hormones of pregnancy * Follicles & corpus luteum  Ovarian artery  Palpated rectally in cows, mares * Determines when to breed

Question 44

Oogenesis

Answer 44

*During fetal development meiosis begins but stops in prophase 1 *After puberty, primary oocytes complete meiosis 1 --produces a secondary oocyte and a first polar body ---- first polar body may or may not divide again *Secondary oocyte begins meiosis 2 but stops in metaphase * Secondary oocyte and first polar body are ovulated (Meiosis 2) * After fertilization meiosis 2 resumes. -- The oocyte splits into an ovum and second polar body * The nuclei of sperm cell and the ovum unite forming a diploid zygote

Question 45

Trace Sperm through reproductive tract

Answer 45

1) Sperm starts in testicle 2) Stored in epididymis 3) Vas Deferens (ejaculation) 4) Prostrate gland 5) Urethra

Question 46

Ovarian Cycle physiology

Answer 46

 Development of ovum, ovulation, formation of corpus luteum, and degeneration of immature follicles and corpus luteum  Influenced by follicle stimulating hormone (FSH) and luteinizing hormone (LH)  Ova are not constantly produced in ovaries  Cyclical sequence of events under influence of FSH and LH

Question 47

The Ovarian Cycle in different species

Answer 47

 Uniparous species * Ovaries produce one mature ovum per cycle * Horses, cattle, humans  Multiparous species (litter species) * Ovaries produce multiple ova per cycle * Cats, dogs, and sows give birth to a litter

Question 48

Primary Follicle

Answer 48

*Immature oocyte surrounded by single layer of flattened follicular cells *Follicular activation

Question 49

Growing Follicle

Answer 49

*Occurs once primary (primordial) follicle has become activated *Oocyte starts to grow in size * Glycoprotein zona pellucida layer forms * Granulosa cells multiply *Antrum is formed

Question 50

Comparative Anatomy Male Accessory Reproductive Glands

Answer 50

Boar- -Seminal Vesicles: Yes, Bulbourethral: Yes Bull-Seminal Vesicles: Yes, Bulbourethral: Yes Cat-Seminal Vesicles: No, Bulbourethral: Yes Dog: Seminal Vesicles: No, Bulbourethral: No Human: Seminal Vesicles: Yes, Bulbourethral: Yes Ram: Seminal Vesicles: Yes, Bulbourethral: Yes Stallion: Seminal Vesicles: Yes, Bulbourethral: Yes Prostrate Gland, all species

Question 51

Mature Follicle

Answer 51

*Oocyte sits in mound of cumulus oophorus *Zona pellucida is surrounded by corona radiata *Estrogen is at peak level

Question 52

Ovulation

Answer 52

*Mature follicle ruptures * Gamete released into oviduct – now called an ovum *Empty follicle fills with blood to form corpus hemorrhagicum

Question 53

Ovulation Stages

Answer 53

Primary Follicle Growing Follicle Mature Follicle Ovulation Corpus Luteum

Question 54

Corpus Luteum

Answer 54

*Formed from cells lining corpus hemorrhagicum *Produces the progestins needed to maintain pregnancy if ovum is fertilized

Question 55

Corpus Luteum

Answer 55

 If pregnancy occurs, remains for entire pregnancy  If pregnancy does not occur, degenerates after a short period  False pregnancy (pseudocyesis) * Common in dogs

Question 56

Ovulation occurs

Answer 56

 Occurs spontaneously in most species * Result of rising levels of LH  Induced ovulators * Ovulation occurs after breeding * Cats, camels, rabbits, ferrets

Question 57

Oviducts

Answer 57

= Fallopian Tubes = Uterine Tubes  Guide ova from ovary to uterus  Serve as usual site for fertilization of ova by spermatozoa  Extend from tips of uterine horns  Fimbriae “catch” ova in infundibulum --- Infundibulum: enlarged opening at the ovarian end of each oviduct ----muscular projections form margin of infundibulum; help properly position infundibulum  Linings covered with many cilia  Move ova down toward uterus

Question 58

Uterus

Answer 58

 Also called the womb  Where zygote implants and grows  “Litter species” have more horn than body * Dogs, cats, pigs  3 layers *Endometrium – site of zygote implantation * Myometrium – thickest layer *Perimetrium  Hollow muscular organ, usually Y-shaped  Forms part of placenta and afterbirth

Question 59

Comparative Female Reproductive Anatomy

Answer 59

All species have the same part Uterine horn in litter species is smaller than in non-litter species

Question 60

3 Layers of Uterine Wall

Answer 60

 Endometrium: lining composed of simple columnar epithelium and simple tubular glands *Secrete mucus and other substances  Myometrium: thick layers of smooth muscle  Perimetrium: outermost layer covered by the visceral layer of peritoneum

Question 61

The Cervix

Answer 61

 Smooth muscle sphincter between body of the uterus and the vagina  Normally tightly closed/Naturally open on only 2 occasions *Estrus (true heat) ---Sperm in *Parturition (birthing) ---Newborns out  Muscular valve that seals off uterus

Question 62

The Vagina and the Vulva

Answer 62

 Vagina * Muscular tube that receives penis during breeding time *Acts as birth canal at parturition  Vulva (External Genitalia) *Vestibule – urethra opens on floor of vestibule * Clitoris * Labia

Question 63

Female Reproductive Physiology

Answer 63

 Puberty – age at which reproductive organs become functional  Males * Quite often mature later than female *Always ready for breeding  Females * Usually mature first *Are only fertile and receptive for a brief time

Question 64

Estrous Cycle

Answer 64

= Heat Period = Estrus  Definite period in each reproductive cycle when breeding can take place  Time from the beginning of one heat period to the beginning of the next  Controlled by 2 anterior pituitary hormones * Follicle stimulating hormone (FSH) (from pituitary) ---- Oogenesis * Luteinizing hormone (LH) (from pituitary) ---- Ovulation, corpus luteum production

Question 65

3 female tracks exit caudally

Answer 65

Dorsal to ventral Digestive Reproductive Urinary

Question 66

Proestrus

Answer 66

 The “building up” phase (7 days)  Blood spotting starts (Day 1)  Follicles begin developing  Estrogen output increases  Blood supply to ovaries increases

Question 67

Estrus

Answer 67

 “True heat” (7 days)  2nd stage of Estrous after proestrous  Estrogen level production peaks  Female sexually receptive  Bloody discharge lighter (straw colored?)  Ovulation! (one or multiple ova) * Ovulation occurs near end of estrus in some species  Induced ovulator species (e.g., cat, rabbit) remain in a prolonged state of estrus if not bred

Question 68

Trace an egg Cell

Answer 68

1. Ovary 2. Oviduct 3. Uterine horn (zygotes) 4.body of uterus 5. cervix 6. vagina

Question 69

Metestrus

Answer 69

 7 days  Time when corpus luteum develops  Lining of uterus thickens for implantation  Progesterone produced by corpus luteum temporarily inhibits follicular development in the ovary  Cornified epithelial lining that developed in the vagina during proestrus and estrus is lost

Question 70

Diestrus

Answer 70

 Corpus luteum at maximum size and exerting maximum effect  If fertilized ovum implants, corpus luteum is retained well into the pregnancy  If no pregnancy occurs, corpus luteum degenerates at the end of diestrus --- sometimes Pseudocyesis, or pseudopregnancy (common in dogs) *Animal then either goes back into proestrus or ovary shuts down and animal goes into anestrus  Seen in seasonally polyestrus animals (cat, horse, cattle, swine)

Question 71

Anestrus

Answer 71

 Period of temporary ovarian inactivity  Seen in seasonally polyestrus, diestrous, and monoestrous animals  Ovary temporarily shuts down  Ovarian inactivity (5+ months in dogs)  Period between breeding cycles

Question 72

Types of Estrous Cycles

Answer 72

 Polyestrous: animals that cycle continuously throughout the year if they are not pregnant (cattle and swine)  Seasonally polyestrous: animals with seasonal variations in estrous cycles (horse, sheep, cat)  Diestrous: animals with two cycles per year, usually spring and fall (dog)  Monoestrous: animals with one cycle per year (fox and mink)

Question 73

cats/rabbits fertility

Answer 73

 Seasonally polyestrus (10 months)  Anestrus (2 months)  Induced ovulators * Need 2 stimuli  Post-partum estrus * Can have 3 litters per year

Question 74

Species specific Estrus

Answer 74

 Time Intervals *Polyestrous --Cattle, swine *Seasonally polyestrous --Horses, sheep, cats * Diestrous ---Dogs * Monoestrous ---Foxes, minks

Question 75

Breeding dogs

Answer 75

 Breed twice when ovulation is occurring  Eggs only in oviduct 72 hours  Sperm only live for 72 hours  Best time to breed?c Day 10 – Day 12  Vaginal cytology *Best way to detect ovulation

Question 76

Glycoprotein zona pellucida

Answer 76

Forms around the growing follicle Thick extracellular matrix composed of glycoproteins to which sperm attach

Question 77

antrum

Answer 77

Fluid-filled space within an ovarian follicle

Question 78

Vaginal tunics and Testis capsule

Answer 78

▪ Tunics are derived from the abdominal peritoneum -- The parietal vaginal tunic forms a grossly visible fibrous sac around each testis and spermatic cord -- The visceral vaginal tunic tightly adheres to the testes – it is not grossly visible ▪ testis capsule: ➢ Is located beneath the vaginal tunics ➢ It is also known as the tunica albuginea ➢ Is composed of dense fibrous connective tissue ➢ Provides support and protection for the testis ➢ Sends branches into the testis that divide it into microscopic lobules, each containing seminiferous tubules and interstitial cells

Question 79

Prostrate Gland

Answer 79

▪ Single structure that more or less surrounds the urethra ▪ Multiple ducts carry its secretions into the urethra ▪ It is present in all common domestic animals ▪ In dogs, it is particularly large because it is the only accessory reproductive gland they have

Question 80

Seminal vesicle

Answer 80

▪ Ducts from the two seminal vesicles (also known as vesicular glands) enter the pelvic urethra in the same area as the vas deferens ▪ They are present in all common domestic animals except for cats and dogs

Question 81

Bulbourethral glands

Answer 81

▪ The paired (two) bulbourethral glands are also known as Cowper’s glands ▪ They are located further caudally than the other accessory reproductive glands ▪ Their ducts enter the urethra back near the caudal border of the pelvis ▪ They secrete a mucinous (mucus-containing) fluid just before ejaculation that clears and lubricates the urethra for the passage of semen ▪ They are not found in dogs

Question 82

How does the reproductive system differ from other body systems?

Answer 82

*Not about survival of the species *Involves a second animal