Male and Female Reproduction

Testes

Produce sperm and testosterone

Epididymis

• Passageway of sperm from testes to vas deferens

• 3 parts: head, body, tail

Vas deferens

Transport sperm from testes to penis (during ejaculation)

Accessory sex glands

Secrete components of seminal fluid

Penis

Fibroelastic or vascular type

Overall functions of the male

• Produce and maintain supply of sperm (spermatogenesis)

• Detect females in estrus (pheromones, visual cues)

• Inseminate females and fertilize the female gamete)

Spermatic cord

Contains vas deferens, pampiniform plexus, and external cremaster muscle nerves

Tunica albuginea

Connective tissue which holds testis together

Seminiferous tubule

Sperm producing cells— true germinal epithelium

Rete testis

Function in sperm transport from seminiferous tubules- 100 tubules

Caput epididymis

Function in maturation of spermatozoa, fluid absorption

Corpus epididymis

Maturation of spermatozoa

Cauda epididymis

Final maturation and storage, only sperm capable of fertilization

Efferent ducts

6-12 tubules absorb fluid

Scrotum

Protection and temperature regulation

Leydig cells (LC)

Source of testosterone

Mitosis (proliferation)

Spermatogonia undergo multiple divisions to generate a larger number of spermatocytes

Meiosis 1 and 2

Replication of DNA to produce haploid spermatids

Differentiation

No further cell divisions, resulting in a fully differentiated immature sperm (spermatids) that is released into the lumen

Mediastinum

In center of testes, transport spermatozoa from lobules within testes to epididymis

Transport from epididymis to penis

1. Exit epididymis and enter vas deferens

2. Vas deferens becomes urethra once past bladder

3. Pass accessory glands that secrete components of seminal fluid

Accessory glands examples (in chronological order)

Ampullae

Seminal vesicles

Prostate

Cowper’s gland

Penile configuration in body

1. Retained in body until excitation/ejaculation

2. Compressed into sigmoid flexure (s-shaped curve) by the retractor penis muscle

   1. Horses do not have sigmoid flexure

3. At excitation, the retractor penis muscle relaxes to extend penis for mating

Fibroelastic penis

• Fibrous, hard sheath of connective tissue all the way through the penis

• Penis does not expand in diameter during erection, it becomes rigid and extends

• Boar, bull, ram

Vascular penis

• Penis increases in diameter and length when aroused

• “Bells out” to plug cervix of female during ejaculation

• Stallion and men

Flehmen response

• Scent driven stimulation

• Exposure of vomernasal gland

Visual/auditory/tactile stimulation

Animal can be trained to mount live animals or (simulation animal— SA) dummies for breeding and/or collection of semen

Volume and sperm concentration

• Inversely related

• Concentration of semen depends in whether specie is a multiple ovulatory, as well as the complexity of the cervix

Pendulous testes

• Fibroelastic penis with pointed glans in bull and a small projection (filiform appendage) in sheep

Horizontal testes

Vascular penis with belling glans in stallion

Inverted testes

Fibroelastic penis with spiral shaped glans that will lock into sow cervix

Cryptorchidism

Lack of testis descent into scrotum and thus thermoregulation is absent

Common in boars and stallions

Bilateral cryptorchidism

1. Sterile

2. No spermatogenesis

3. Testosterone is produced

Unilateral cryptorchidism

Fertile

Reduced sperm producing capacity

Temperature of testis for spermatogenesis

3-6 degrees Fahrenheit less than body temperature

5 factors for testis temp regulation

1. Location: testis are outside and away from the body for air circulation

2. Insulation: thin scrotal skin with subcutaneous fat

3. Sweat glands: For evaporative cooling

4. Tunica dartos muscle: smooth muscle under scrotum that can contract to move testis closer or relax to help testis move away from the body

5. Body supply to testis: warm arterial blood is cooled before entering testis by crossing over cooler veins that are leaving testis

Importance of keeping testis cool

Protect sperm

• The farther from the body, the cooler

• The tail of the epididymis is the coolest

• Elevated temperatures will kill sperm cells

• Typically lower sperm count and motility in very high temperatures

Estrous

The reproductive cycle in females that are of an estrual species (bovine, ovine, caprine, porcine, caprine, feline)

Generally calculate from the period of estrus and ovulation to the next period of estrus and ovulation

Estrus (Heat)

The period of time where a female is sexually receptive to the male for purposes of mating

Anestrous period

When a female is not in estrus. Non-breeding season

Estrus synchronization

Controlling the estrous cycle so that a high percentage of females in the herd express estrus at the same time

Clone

An individual grown from a single somatic cell of its parent and genetically identical to it

AI

Abbreviation for artificial insemination, a common technique where semen is placed into the reproductive tract of the female by artificial techniques rather than natural mating

ET

Abbreviation for embryo transfer, a procedure used to transfer embryos from a donor female to a group of recipient females

Haploid

Half the normal number of chromosomes, found in sperm and ova

Open

Refers to non-pregnant females

Fertility

The capacity to initiate, sustain, and support reproduction

Dystocia

Difficult birth, intervention required

Vulva/vagina

Female organ of copulation; birth canal for parturition

Cervix

Passageway for sperm following breeding; seals off uterus during pregnancy

Uterus

Secretory organ; incubator for embryo and placenta; control of cyclicity (leuteolysis which destruction of the corpus luteum); contraction for parturition

Oviduct

Passageway for ovum and sperm; site of fertilization

Ovary

Produces female gamete and female sex hormones (estrogen and progesterone)

Vulva

• Passageway for urine

• Receptor for penis during copulation

• Expands at parturition for delivery of fetus

• Not to be confused with the anus

Interior protective structures of the female reproductive tract

Vagina and cervix: tissue is keratinized to protect against abrasion, secretory, provides barriers

Functions of vagina

• Copulatory organ

  • Fornix vagina is site of semen deposition (cow, ewe)

  • No glands— secretions come from passageway of plasma components as well as cervix

  • Provides lubrication

  • pH us acidic (5.7)— bacteriostatic

• Birth canal

  • Dilates for fetus during parturition

Functions of the cervix

• Composed of cartilage surrounded by soft tissue

• Openings are the external or internal Os

• Passageway for sperm following breeding

• Secretes mucous, seals off uterus during pregnancy

• Passageway of fetus

• Species specific configuration (rings, spiral, or folds)

Cow cervix

• Hard and rigid during estrus

• Composed of thick connective tissue

• Contain crypts which provide surface area for sperm reservoir

• 4-5 annular rings

• Tightly closed except during estrus

• Mucus characteristics change during estrous cycle

  • Estrus: clear, watery parallel strands (estrogen)

  • Diestrus: little mucus, jelly-like mucus cross-linked by disulfide bonds (progesterone)

Fornix vagina

Present in mare, ewe, and cow

Recess in the anterior vagina that surrounds the protruding cervix

Mare cervix

• There are no obstacles in the body after the fornix vagina

• Opposite of other species, it has a soft and pliable cervix during estrus and flattens on floor of vagina

• During pregnancy, cervix is tight and closed

Sow cervix

• Many interdigitating pads

• Does not have fornix vagina

Uterus (womb)

• Incubator for fertilized ovum, nutrients to ovum

• Aids travel of sperm

• Secretory organ

• Has two horns or branches and a single body

• Shape differs between species

Sperm related uterine functions

• Transport sperm

  • estrogen stimulates myometrial contractions so that sperm move to site of fertilization

• Sperm motility

  • Viable sperm (motile) are important so that they are not absorbed

• Partially prepares sperm for fertilization

  • Estrogen stimulates uterine secretions which capacitate sperm (zona pelucida)

Protective uterine functions

• Absorption and phagocytosis

  • Occurs by uterine epithelium and leukocytes which fight infection

• Recovers from pregnancy

  • Uterine involution— myometrial contractions and enzymatic activity shrink uterus back to normal size

• Muscle contractions (kinda different)

  • Towards oviduct during estrus (heat), but following ovulation are towards cervix until progesterone increases from CL

If not pregnant

Uterine endometrium releases prostaglandin (PGF_{2a}) to cause the CL to regress

Fetus related uterine functions

• Provides environment for embryo

  • Uterine secretions stimulated by estrogen and progesterone

  • Proper timing of embryo and uterus is important for embryo transfer

• Supports development of fetus

  • Quiescent myometrium— progesterone

  • Immunological protection from rejection by maternal immune system

• Expels fetus at birth

  • Strong rhythmic myometrial contractions (progesterone low)

If pregnant

Embryo provides a chemical signal (interferon tau) which allows the CL to be maintained

Oviduct

• Tube that connects the ovary to the uterus

• Has 3 distinct regions

  • Infundibulum

  • Ampulla

  • Isthmus

  • Ampulla-Isthmus Junction (AIJ)

Infundibulum

Surrounds ovary with finger-like projections

Ampulla

Transports oocyte

Isthmus

Transports sperm

Ampulla-Isthmus Junction (AIJ)

Site of fertilization

Ovary regions

• Comprised of two main regions

  • Cortex (outer on all— except mare)

    • Produce the female gamete (ovum or oocyte)

      • Released from follicle

    • Includes ovarian structures

      • Produce hormones

  • Medulla (inner in all— except mare)

    • Support tissue including blood vessels and immune cells

Function of the ovary

• Farm animals have TWO ovaries

  • Surrounded by connective tissue called tunica albuginea

• Produces female gamete (the ovum) — largest single cell in the body

• Produces female sex hormones (estrogen and progesterone)

Follicle

Blister-like structure on the ovary that contains ovum and hormone-rich fluid (liquor folliculi)

3 types

Graafian

Mature folicle

Atretic

Deteriorated follicle

Cystic

Continuous corpus luteum, graafian, or atretic structure (may or may not cause clinical signs)

Corpus luteum

• “Yellow body” forms after ovulation

• Produces progesterone which is important for maintaining pregnancy

• Composed of luteal cells that originate from granulosa and theca cells of the Graafian follicle

Function of the corpus luteum

Produce progesterone to:

• Inhibit estrus and parturition

• Block myometrial contractions

• Stimulate stimulate endometrial secretion of nutrients

• Stimulate the production of luteolytic agent to kill the CL if no embryo is present

  • Prostaglandin (PGF_2a)

Structures on the ovary

• Follicles develop on the ovary and mature until one becomes a Graafian follicle

• Follicles not selected for ovulation become atritic and regress

• When oocyte is released from the follicle, follicles will transition through the corpus hemorrhagicum, corpus luteum, and the corpus albicans

Diagram of bull reproductive system (draw)

Structure of the testis (draw)

Testes anterior/posterior halves

Cow reproductive system

Ovarian process diagram

Graafian follicle diagram

Bicorunate

Sow reproductive tract

Bipartite

Cow, ewe, doe reproductive tract

Modified bipartite

Mare reproductive tract

ovulation fossa

Specialized structure on mare ovary to funnel a single ovulation