Animal Reproduction - ANEQ 310 (Set 2)

The Male Reproductive Tract

analogous to a manufacturing complex which produces:

-spermatozoa

-hormones

-proteins & fluids

Hormones that the male reproductive tract produces

-testosterone

-estradiol

The two primary functions of the male reproductive system

1. formation of sperm

2. deposition of sperm into the female rerpductive tract

Types of deposition of sperm into the female repro tract

-natural cover

-artificial insemination (AI)

-in vitro fertilization (IVF)

Spermatic Cord

-suspends the testes in the scrotum

-provides a pathway for blood

-lymph and nervous tissue

-acts as a heat exchanger

Cremaster Muscle

-primary muscle supporting the testes

-contraction & relaxation facilitates blood flow & heat exchange

-not responsible for long term contraction of the testes

Pampiniform Plexus

-complex vasculature created by the entwinement of the testicular artery & vein

-important for temp. control & hormone diffusion

Temperature Control

important for spermatogenesis to occur correctly

How can temperature affect spermatogenesis?

-excessive heat causes degeneration of cells

-cryptorchid: retained testes cannot produce viable sperm

-"short scrotum": artificial shortening of the scrotum reduces spermatogenesis

-extreme climates or summer months: high ambient temps can cause lowered fertility

Scrotal Mechanisms

-cooling mechanisms

-scrotal skin > evaporative cooling

-countercurrent exchange from vascularization

Tunica Dartos

-increases surface area of scrotum & distance from body

-can stay contracted for an extended period of time

-long term temp. control

Where does countercurrent exchange from vascularization occur and what does it do?

-the pampiniform plexus (in spermatic cord)

-testicular vein and artery exchange heat to regulate temperature

Scrotum

-a two-lobed sac which encloses the testes & regulates temp.

-consists of 4 major layers

The 4 major layers of the scrotum

-skin

-tunica dartos

-scrotal fascia

-parietal vaginal tunic

Skin of the scrotum

-a major layer of the scrotum -many sebaceous & sweat glands for evaporative cooling

-thermosensitive nerves control sweating and respiration rate

Tunica dartos of the scrotum

-a major layer of the scrotum

-smooth muscle layer beneath skin helps control temperature by adjusting distance of testes from body

-as it relaxes (lengthens) scrotal surface area increases allowing for greater heat exchange

Scrotal fascia of the scrotum

-loose connective tissue

-allows testis to move freely within the scrotum

Parietal vaginal tunic of the scrotum

-inner most layer of the scrotum

-lines the scrotum

Testes

-paired organs that are considered the primary reproductive organs in the male

-produce male gametes (spermatozoa) & androgen (testosterone)

What hormones do the testes produce?

-inhibin

-estrogen

-a variety of proteins important for spermatozoa production

Do testes only produce sperm and hormones?

No, they also produce seminal fluids.

Are gametes present at birth for males?

-No. They differ from female ovaries in that gametes are not present at birth.

-New spermatozoa are produced beginning with the onset of puberty .

Testes Development

-in-utero development

-Y-chromosome codes for the production of testis determining factor (TDF)

-form inside the body cavity

-descend through the inguinal canals into the scrotum during gestation

What does testis determining factor (TDF) determine?

it determines the development pathway

Ligamentous gubernaculum

-attaches testes to the peritoneum

-as fetus grows, testes are pulled through inguinal canals into the scrotum

What does cryptorchid mean?

when testis(es) fail to descend normally

What does it mean if a male is bilaterally cryptorchid or unilaterally cryptorchid?

Bilateral: sperm will be sterile due to heat

Unilateral: sperm will be fertile

Testicular Capsule is made up of these

-visceral vaginal tunic (VVT)

-tunica albuginea (TA)

-together thought to provide pumping action facilitating movement of sperm during spermatogenesis

Visceral Vaginal Tunic (VVT)

-superficial anatomy of the testes

-makes up the testicular capsule

-serous tissue

-covers the testis in all species

-extension of the peritoneum

Tunica Albuginea (TA)

-superficial anatomy of the testes

-makes up the testicular capsule

-thin, white membrane of connective tissue

Parenchyma

-part of functional anatomy of the testes

-cellular mass of gland or organ, supported by connective tissue

What does the tubular compartment of the testes contain?

seminiferous tubules

What does the interstitial compartment of the testes contain?

-blood vessels

- connective tissue

-lymphatics

-nerves

-Leydig cells

Seminiferous Tubules (ST)

-functional layer of testes

-occupy the most space in the testes

-contain nurse cells (Sertoli Cells)

-site of spermatozoa production

-contain germ cells (spermatogonia)

What are the two major regions of the Seminiferous Epithelium?

1. Adluminal

2. Basal Compartment

What separates the compartments of the Seminiferous Epithelium?

Compartments are separated by tight junctions between Sertoli cells. These junctions form the blood-testis barrier that protects developing sperm from immune system

Rete Testis

-network of tubules

-receives spermatozoa from the seminiferous tubules & transports it out of the testis

Efferent Ducts

-12 to 15 ducts

-receive spermatozoa from rete testis

-converge into the head of the epididymis

-converge to single duct > epidydimal duct

What is the Epididymis responsible for?

-transport

-concentration

-storage

-maturation

What are the 3 distinct regions of the Epididymis?

1. Head (Caput)

2. Body (Corpus)

3. Tail (Cauda)

-rhythmic contraction of smooth muscle move spermatozoa toward tail

What happens to spermatozoa coming into the epididymal ducts?

-they are diluted by rete fluid

-most rete fluid is absorbed by epithelium of the efferent ducts & proximal head of epididymis

What is the primary storage site for spermatozoa in the epididymis?

the tail (cauda)

After repeated ejaculations, are sperm concentrations the same?

No - high ejaculation rate decreases sperm concentrations by 25-45%

-can be reduced to zero

What happens to overflow of spermatozoa? Are they reabsorbed by the testes?

No, they are not reabsorbed - periodic contractions move overflow from epididymis into urethra for excretion in urine

How long can spermatozoa be stored for?

studies have shown storage can be up to 60 days

Where do spermatozoa mature?

-as they move through the epididymis

-proteins and other molecules that bathe sperm change with each stage along the epididymal duct

Are sperm entering the head of the epididymis fertile?

No

What migrates to the tail of the epididymis as spermatozoa matures?

cytoplasmic droplet at the base of the head

Are sperm in the tail of the epididymis fertile?

Yes, they are fertile and ready for ejaculation

Vasa Deferentia (singular form = Vas Deferens & Ductus Deferens)

-part of the spermatic cord

-a pair of ducts that connect the left & right epididymis to the ejaculatory ducts

What is the function of the Vasa Deferentia?

only purpose is to transport sperm to the urethra for expulsion during ejaculation

Vesicular Glands (Seminal Vesicle)

paired glands that contribute large proportion (up to half) of ejaculate secretion volume

Where do secretions of the Vesicular Glands enter?

-accessory gland

-where the vas deferens merges with the urethra

-fructose &

sorbitol

-source of energy for spermatozoa

Prostate Gland

-accessory gland

-produces semen & compounds that protect sperm from acidity of female repro tract

Is the shape and the location of the prostate gland the same in every species?

No- shape and location varies greatly between species

Where does the prostate gland usually sit (even though location differs between species)?

usually sits at the junction between the bladder and urethra

Bulbourethral Glands aka Cowper's Gland

-accessory gland

-paired

-located on either side of urethra

-produce viscous secretion that forms coagulate following ejaculation (vaginal plug)

What are the functions of the Bulbourethral Glands?

-lubricates urethra for ejaculate to pass through

-secretions flush urine residue from urethra

-contribute very little to the overall volume

Penis

organ of copulation and is composed of 3 parts

The Base of the Penis

the attachment to the pelvis

The Shaft of the Penis

the main portion of the penis

The Glans of the Penis

-the specialized distal end

-special species specific adaptations to penetrate cervical interdigitations

Rams have this type of penis

filiform appendage

Boars have this type of penis

corkscrew shape

Stallions have this type of penis

more erectile tissue than other farm species

Sigmoid Flexure

-found in species with fibroelastic penis (i.e. bulls, boars, and rams)

-retractor penis muscle

T/F: The bull has a fibroelastic penis with a lot of erectile tissue and a sigmoid flexure.

False - The bull has a fibroelastic penis with limited erectile tissue and a sigmoid flexure

T/F: The stallion depends upon erectile tissue which fills with blood upon sexual stimulation.

True