Reproduction unit

Includes all the lectures from repro

Reproduction

 The process by which animals produce offspring

It is a sequence of events. 

What is the sequence of events for repro?

1. 1. Begins with the development of the embryo and reproductive system.

2. 2. The animal is born and grows and develops throughout its lifetime.

3. 3. What occurs after copulation within the male and female reproductive tracts.

4. 4. The pregnancy and gestational periods.

5. 5. During and after lactation (in mammals)

Sexual reproduction in animals

 Gametes require 2 parents and apply to most animals. Sperm is the sex cell of male animals, produced in the testes. The egg (ovum) is the sex cell of female animals, produced in the ovaries

Asexual Reproduction

occurs without the interaction of cells or gametes; no mates required, no exchange of genes with another mate through sex. Some examples of organisms that reproduce asexually are bacteria, fungi, various plants, and some animals (zebra sharks, boa constrictors, starfish, etc.)

Gonads

 sex organs (produce reproductive cells). Critical for sexual reproduction; males = testes, producing sperm for most of life. Females = ovaries, release egg cells; mammals are born with all egg cells

Fertilization

is the fusion of the haploid egg and sperm to form the diploid zygote. Diploid: two sets of genes (haploid = one). This process can occur naturally within the body or through reproductive technologies outside the body. Example: in-vitro fertilization

Implantation

is a process in which a developing embryo, moving as a blastocyst through a uterus, makes contact with the uterine wall and remains attached to it until birth. The lining of the uterus (endometrium) prepares for the developing blastocyst to attach to it via many internal changes. Without these changes, implantation will not occur, and the embryo sloughs off during menstruation 

natural insemination

When male and female mate, sperm is placed in the female’s reproductive tract by copulation, or the mating process.

artificial insemination

Placing semen collected from a male in the female reproductive tract with special equipment.

Gestation

The time during which the embryo/fetus is developing in the uterus; occurs throughout the duration of pregnancy

parturition

The process of giving birth or the delivery of the fully grown fetus. Signifies the termination of pregnancy and the beginning of extrauterine life

sexual classification

The condition of an animal based on its age and sexual condition. Useful to describe animals. Includes animals that are both capable and incapable of reproduction

Castration

Removal of testes from the male. Used on young male animals. Promotes growth and development in more desirable ways. 

Gestation of Cows

about 274- 291 days

Gestation of sows

about 115 days

Gestation of ewes

about 140-160 days

gestation of does

about 145-155 days

Gestation of mares

about 330- 342 days

gestation of dogs

about 58-65 days

gestation of cats

about 58-67 days

Male reproductive responsibilities

• Produce viable sperm in viable amounts and deliver sperm to the vagina or collection receptacle.

Testis with seminiferous tubules

 sperm production

Epididymis

transport, maturation, and ejaculation

vas deferens (sperm Duct)

 transport and ejaculation

Seminal vesicles

 secrete thick liquid to transport sperm

Prostate gland

 Secretes a thick alkaline solution to neutralize urine and the female system

Cowepers gland

secretion may lubricate, flush out urine, or form a gelatinous plug

Penis

copulation

Scrotum

Sack that holds the testicles

Along with holding what does the scrotum do?

Protects the testicles

Why is it outside the body?

The temperature of the testicles needs to be cooler than the inside of the body

Testicles

The male sex organ that produces sperm

What is the temperature difference in the scrotum

4 to 6 degrees C cooler than typical body temperature

How does it develop?

Starts in the abdominal cavity. Then descends into the scrotum through the inguinal canal.

What is cryptorchidism

Failure of the testis to fully descend into the scrotum.

What is unilateral crypto?

only one does not descend

What is bilateral crypto?

both do not descend

What does bilateral crypto mean for fertility?

The animal is sterile

What is abdominal crypto?

Does not descend at all

Where is it retained?

in the inguinal canal

Who is it most common in?

Boars – Dogs – stallions

Who is it least common in?

Bulls – Rams – Bucks

testis structure

Seminiferous tubules, Tunica albuginea, Tunica dartos, Spermatic cord

Spermatic cord

Location of the vas deferens, cremaster muscle, and pampiniform plexus 

Seminiferous tubules

where sperm is made

Tunica albuginea

 Connective tissue that provides structure

Tunica dartos

smooth muscle; aids in temperature control

Spermatic cord summary

Aids in suspension of the testes; “Air conditioner”

Pampiniform Plexus

Network of blood vessels, Majority of the spermatic cord, Vascular heat exchange, Hormone exchange, Pulse regulation

Vas Deferens

Small tube: connective tissue from epididymis to urethra

Vasectomies

removal of a portion or tying off the Vas deferens

Cremaster Muscle

Primary support of the testes, Skeletal muscle, cannot support sustained contractions, cycles blood from testis and body cavity

epididymis

Concentrates, stores, transports, and facilitates maturation of sperm

3 parts of the epididymis

Seminiferous tubules: where sperm is made; Head of Epididymis: Where sperm is concentrated; Body of Epididymis: Where sperm matures; Tail of Epididymis: Where sperm is stored until ejaculation

Vas Deferens

Tube that transports mature sperm. Connection from the epididymis to the urethra.

Accessory glands

Seminal vesicles,  Prostate, Bulbourethral (Cowper’s) gland

Bulbourethral (Cowper’s) gland

 Secretes mucus during arousal for lubrication of the urethra; aids in semen transport

prostate

Produces 30% of semen; surrounds the prostatic urethra

Seminal vesicles

Produces 65% of semen; joins with the vas deferens in the ejaculatory duct

Fibroelastic penis

limited erectile tissue encased in a non-expandable, dense connective tissue structure

Sigmoid flexure

•  S-shaped configuration along the shaft

• Allows the penis to be retracted inside the body until an erection occurs

• Retractor penis muscles

contracted

held inside the sheath

relaxed

penis protrudes

Vascular penis

• Contains vascular tissue

• Fills with blood to sustain erection

• NO sigmoid flexure

where is the rooster repro tract at

Situated along the back of the bird.

Rooster reproductive tract

• Larger when bird is actively mating.

• Controlled by light availability.

• Connected to the digestive tract at the cloaca.

• Production of sperm stimulated by light.

• Light triggers hormone production in the brain.

• It works the same way for hens!

• No penis.

• Instead there is a “rudimental penial organ.”

• Functions similarly to a penis.

Testosterone

 Produced in the testes, Production triggered by pituitary gland, causes secondary sex characteristic development, Stimulates sperm cell development

Luteinizing Hormone (LH)

Helps signal testosterone production

Follicle-Stimulating Hormone (FSH)

Stimulates sperm production, an indicator of sperm health

Female Reproductive Responsibilities

1) Produce a viable ovum and release it at the correct time.

2)Successfully conceive (union of sperm and egg)

3)Provide for the fetus during pregnancy

4)Successfully deliver the fetus

5)Accept and nourish the newborn

Ovary

Produce oocytes

•A cell in an ovary which may undergo meiotic division to form an ovum

Production of estrogen (Graafian follicle) – mature follicle

Production of progesterone (Corpus Luteum) – ruptured follicle

Follicles

•Blister-like structures

•Contain ovum (ova)

•Very immature follicle

Folliculogenesis

•an immature follicle develops into a more advanced follicle and becomes a “candidate” for ovulation

1.Primordial Follicles

•Most immature and are the smallest encountered in the ovarian cortex

1.Primary Follicle

•Slightly more advanced

•Surrounded by a single layer of epithelial cells

Secondary Follicle

•Two or more layers of follicle cells, without a cavity

Surrounded by a thick translucent layer called zona-pellucida

Tertiary Follicle (Developing Antral Follicle

•Fluid filled cavity -- contains follicular fluid

•Can usually be observed with the naked eye

Graafian follicle

mature follicle

Corpus Luteum

•“Yellow body” (yellow mass of cells)

•Produces progesterone.

•Steroid hormone responsible for the decidualization of the endometrium (its development) and maintenance, respectively.

Essential for establishing and maintaining pregnancy in females

Corpus Albicans

•“White body”

•Degenerated Corpus Luteum

•Scar-like structure (does not directly impact fertility)

•Presence and function are indicators of a healthy reproductive system

•Formation of the corpus albicans signifies…

1.Ovulation has occurred

Required hormonal changes have taken place.

Corpus Albicans functions

-Provide structural support to the ovary

-Minimal function with maintenance of  hormonal balance

oviduct

•Transport ova and sperm

•Site of fertilization and early cleavage

•Cleavage: early division of cells

•Remember:

•Zygote starts as a fertilized cell

•Divides very rapidly before arriving in the uterus

uterus

•Assist sperm transport

•Sperm must get to oviduct!

•Regulation of corpus luteum

•Glandular secretions nourish embryo

•At least, until the placenta forms

What happens in the uterus

•Site of implantation and pregnancy

•Expulsion of fetus and fetal membrane at birth

•This includes the placenta

Duplex uteruses

Two uterine horns each with separate cervical canal opening directly into the vagina

Bicornuate uterus

Small uterine body and tow long uterine horns. The upper parts of the uterus remain separate, but the lower parts are fused into a single structure

bipartite uterus

Prominent uterine body and two uterine horns. Share single cervix

simplex uterus

Pear shaped body with no uterine horns. Entire uterus is fused into a single organ

cervix

•Facilitating sperm transport

•Example: sow

•Goes through morphological changes

•Prevent uterine contamination

Vagina

•Copulation organ

•Birth canal

•Fetus must pass through

•Uterine membranes are also expelled

Hen reproductive tract

•Ovary developing many follicles at once

•Follicles in different developmental stages

•Yolk is developed follicle (ovum)

•Released into infundibulum

•Fertilization not required for egg to form

•Other egg components added as the ovum travels through the oviduct

•Albumen

•Shell membrane

•Shell

•Shell pigment

•Etc…

Estrous

•Is an Adjective

•The CYCLE of ovulation in females

•Development of a mature follicle

•Characteristic of reaching puberty

•Length of estrous is species dependent

estrus

•Is a Noun

•Standing Heat

•Phase of sexual receptivity

•The act of ovulation (expulsion of ova)

follicular phase

•The phase from regression of the CL to Ovulation

•About 20% of the estrous cycle

•Large antral follicles = the primary ovarian structure

•Estradiol = the primary hormone present

luteal phase

•The phase from ovulation until the regression of the CL

•About 80% of the estrous cycle

•Corpus luteum = the primary ovarian structure

•Progesterone = the primary hormone present

three types of estrous cycles

1.Polyestrus

2.Seasonally polyestrus

3.Monoestrus

polyestrous

Animals that cycle continuously throughout the year if they are not pregnant

seasonally polyestrous

Animals with seasonal variations in estrous cycle. Continuously cycle during a specific season

monoestrus

Animals with once cycle per year

diestrus

Animals with two cycles per years, usually one in spring and one in fall.