Spermatogenesis

Where will the testis be located in bull, ram, stallion, camel?

Ingunial

Where are the testis of the boar, dog, and tomcat located?

Perineal

What are the components of the scrotum?

•Testes

•Epididymis (Caudus, corpus, caput)

•Vas deferens (deferent duct)

T/F The testes develop inside the body

True

What is Cryptorchidism?

failure of the testes to descend into scrotum

Where are testicles usually retained in Cryptorchidism?

abdomen or inguinal canal

T/F Cryptorchidism is more common in toy and miniature breeds

True

T/F Spermatogenesis requires temperatures ~10F cooler than body temperature

False 4-6° cooler than body temperature

Testicular veins create an elaborate network and wrap around the artery, what is this called?

pampiniform plexus

What muscle contracts and relaxes to promote venous return of testicular blood?

Cremaster muscle

What is the scrotal skin heavily populated with? What type of nerves innervates these glands?

sweat glands innervated via sympathetic nerves

When male experiences elevated temperatures it sends nerve impulses to sweat glands, the skins is populated with high numbers of thermosensitive nerves.

What do these nerves signal to happen?

tell the body to increase respiratory rate to induce panting

Birds, elephants, sloths, armadillos, whales and dolphins have what kind of testes?

internal or retroperitoneal testes

T/F Rats and rabbits have testes that move into and out of body cavity

True

What is the primary reproductive organ in males?

What does it produce

Testes

Produce

•Spermatozoa

•Hormones and proteins

•Fluids

T/F The testes is most similar to the ovary

True

Testicular parenchyma consists of what?

•Seminiferous tubules

•Leydig cells

•Capillaries

•Lymphatic vessels

•Connective tissue

T/F The testicular parenchyma is also divided into two compartments: tubular and interstitial

True

What are the compartments that the Seminiferous Tubules divide into?

•Basal compartment

•Adluminal compartment

What does the basal compartment house?

Houses spermatogonia and primary spermatocytes

What separates the basal compartment?

Separated by tight junctions of Sertoli cells

What does the Adluminal compartment house?

Houses maturing spermatocytes/spermatids

What forms the Blood Testes Barrier?

•Formed by the tight junctions connecting the Sertoli cells

What separates the adluminal compartment from basal compartment?

Blood Testes Barrier

What does the Blood Testis Barrier (BTB) help to protect?

•Protects post-meiotic germ cells (spermatocytes, spermatids, and sperm) from cytotoxic agents

The BTB creates an _____-______ ____ in testicular epithelium to allow for what process to occur?

immune-privileged site

meiosis of spermatocytes

What are the FOUR goals of spermatogenesis?

1. Provide a continual supply of male gametes (for up to decades) through stem cell renewal

2. Provide genetic diversity

3. Provide billions of sperm each day (domestic animals) to maximize reproduction by both natural service and artificial insemination

4. Provide an immunologically privileged site where developing germ cells are not destroyed by the male's immune system

What is the "equation for spermatogenisis"?

Spermatogenesis = proliferation + meiosis + differentiation

T/F Spermatogenesis has 5 Phases

False, 3 phases

What are the 3 phases of Spermatogenesis?

Proliferation phase

Meiotic phase

Differentiation phase

What is another name for the proliferation phase?

spermatocytogenesis

What is another name for the Differentiation phase?

spermiogenesis

T/F All mitotic divisions occur durning Spermatocytogenesis

True

When does Spermatocytogenesis begins?

begins at puberty

yall need to look at how these lil shytes divide in the pictures in the lecture during Spermatocytogenesis

sorry im lazy :)

After, final division spermatogonia destined to differentiate cross what?

BTB

What phase during spermatogenesis does meiosis occur?

Meiotic Phase

Durning the Meiotic Phase, where will the spermatocytes be/start?

Spermatocytes have successfully crossed BTB into adluminal compartment

T/F Primary spermatocytes immediately enter Meiosis II

False, Meiosis I

Unlike oocytes, meiosis creates how many total cells

4 cells

What do spermatocytes become during the meitoic phase?

spermatids

Approx how many days are the following stages of Spermatogenesis?

Proliferation phase (spermatocytogenesis)

Meiotic phase

Differentiation phase (spermiogenesis)

Proliferation phase: 21 days

Meiotic phase: 23 days

Differentiation phase: 17 days

(about 61 days in total)

What occurs in Spermiogenesis (Differentiation Phase)?

Creates a sperm cell potentially capable of traveling to and fertilizing an egg

How many phases are there during the Differentiation phase (Spermiogenesis) ? What are they?

4 phases:

Golgi phase

Cap phase

Acrosomal phase

Maturation phase

T/F The golgi phase starts with the development of the poor golgi apparatus

False, Starts with a well defined Golgi apparatus

During the golgi phase, Vesicles of the Golgi begin to fuse and create what?

pro-acrosomic granules

The Vesicle fusion continues until a large _____ _____ is formed

acrosomic vesicle

What migrate beneath the nucleus and will become attachment point for tail?

Centrioles

What occurs during the cap phase?

Acrosome forms a distinct cap over the nucleus

T/F Once the cap is added, the golgi moves away and disappears and then primitive flagellum begins to project

True

During the Acrosomal Phase, Acrosome spreads to cover _/_ of the _____ nucleus

2/3

anterior

What other thing forms in the Acrosomal Phase?

neck forms

During the maturation phase, what MAIN things is happens?

Mitochondria accumulate around flagellum

(Creates a "middle piece" of sperm)

Mature sperm is composed of a ____ and ____

head

tail

What makes up the head of the sperm?

Head = nucleus + acrosome + post-nuclear cap

What makes up the tail of the sperm?

•Tail = middle piece + principle piece + terminal piece

Spermiation is the release of _____ from the Sertoli cells into the lumen of the ______ _____

spermatozoa

seminiferous tubules

What are the important parts of spermatozoa?

Nucleus (oval, flattened, and chromatin is highly compacted)

Transcription and translation stopped so DNA at this point is “inert” until fertilization

Acrosome – “cap” filled with hydrolytic enzymes necessary to penetrate oocyte

Mitochondria - produce energy for the movement of the sperm

(Rapidly degraded after fertilization)

T/F Spermatozoa can fertilize an egg

FALSE, IT CANNOT

T/F Even though spermatozoa are continually released, spermatogenesis occurs in cycles

True

The cycle of the _____ _____ is the progression through a complete series of spermatogenesis stages at one location along a seminiferous tubule

seminiferous epithelium

Why did the hypothalamus break up with the testes?

Because it said, “You’re too dependent—I need some negative feedback!” 😆

onto Endocrine regulation of spermatogenesis

Spermatogenesis requires three different secretions from three different sections of the HPG axis, what are they and where do they occur?

•Secretion of GnRH from hypothalamus

•

•Secretion of FSH and LH from anterior lobe of pituitary

•

•Secretion of gonadal steroids

T/F The gonads in the male only secretes testosterone

False, Testosterone AND estrogen

T/F GnRH released in intermittent bursts throughout day and night

True

LH pulses almost immediately after the _____ burst and last 10-20 minutes

GnRH

FSH also follows GnRH bursts but at higher concentrations than LH and for longer periods

False, lower

What does LH act on in the testes?

Leydig cells

What are the Leydig cells analogous to in the female?

Analogous to the theca cells of the ovary

When activated by LH, Leydig cells converts what to what?

progesterone to testosterone

Leydig cells secrete testosterone which gets transported to the ____ ______

Sertoli cells

What hormone acts of the sertoli cells of the testes?

FSH

•FSH tells Sertoli cells to initiate what?

spermatogenesis

T/F After initiation of spermatogenesis, Sertoli cells become less responsive to FSH and more responsive to testosterone

True

What secreted by Leydig cells tells Sertoli cells to maintain spermatogenesis

Testosterone

What are the sertoli cells analogous to in the female?

Analogous to the granulosa cells of the ovary

•When activated by FSH, Sertoli cells convert what to what?

testosterone to estradiol

(•Thought to play a role in negative feedback on hypothalamus)

What cells secrete inhibin and what does it do?

Sertoli cells

suppress FSH secretion from pituitary

T/F Spermatozoa has been successfully released to lumen of seminiferous tubule, it can now fertilize eggs

False, still cannot

Once Spermatozoa leave seminiferous tubules and enter what?

rete testes

T/F •Rete testis "mixes" sperm together

True

•Rete testis transports sperm to where?

efferent ducts

•Efferent ducts converge into a single duct – which is called what?

epididymal duct

Where do sperm undergo final maturation stages?

epididymis

T/F Epididymis is one single, highly convoluted tube comprised of 3 sections

true

What are the three parts of the epididymis?

•Caput (head)

•Corpus (body)

•Cauda (tail)

Epididymis surrounded by ____ ____ which produces rhythmic contractions throughout the duct

smooth muscles

Each species has its own epididymal transit time

theres a chart have fun or dont (slide 58)

Sperm concentration is relatively low when they enter epididymis caput due to high levels of rete fluid, where are the rete fluids from?

sertoli cells

Efferent ducts and caput (proximal head) absorb most of the rete fluid what does this in turn do?m

– concentrates sperm number

The location of what can help identify sperm maturation issues in males?

Cytoplasmic droplet

Cauda smooth muscle remains quiescent until sexual excitation when smooth muscle contracts vigorously to move spermatozoa into _____ _____ for ejaculation

ductus deferens

If no sexual release occurs, periodic contractions occur to move old sperm to _____ ____ and _____ where they are flushed out during urination.

ductus deferens and urethra

What are the FIVE functions of accessory sex glands?

1. Nourish spermatozoa

2. Activate spermatozoa

3. Clear the female reproductive tract

4. Produce secretions that assist in transport to the female reproductive tract

5. In some species, form a plug to help retain spermatozoa in the female reproductive tract

What accessory Sex Gland is an enlargements of ductus deferens that open into pelvic urethra?

ampulla

What accessory Sex Gland is paired glands that empty directly into pelvic urethra?

Vesicular glands (Seminal vesicles)

What are the two different types of prostate glands?

•Corpus prostate - outside of the urethralis muscle (stallion, dog, cat

•Disseminate prostate - distributed along walls of pelvic urethra (ram, boar)

What accessory Sex Gland is:

•Paired glands located on either side of pelvic urethra

•Produce the viscous secretion that causes seminal plasma to coagulate following ejaculation

Bulbourethral glands (Cowper’s glands)

What are the THREE accessory sex glands used for the components of seminal fluid?

Vesicular glands (Seminal vesicles)

Prostate

Bulbourethral glands

What do the Vesicular glands (Seminal vesicles) do when looking at the component of seminal fluid?

Secrete fructose

Prostaglandins

Proteins