Endocrinology of the Male and Spermatogenesis

Animal Sciences 341 with White at University of Nebraska - Lincoln

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By: Cassie Sell
Created: 2010-12-12
Size: 32 flashcards
Views: 5

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Production of fertile spermatozoa requires

endocrine regulation of the testis

meiotic division of spermatogonia

mitotic division resulting in haploid spermatids

morphologic transformation of spermatids into spermatozoa

Endocrine requirements for sperm to be produced

adequate production of GnRH from hypothalamus

FSH and LH secretion from the anterior pituitary gland

secretion of gonadal steroids(testosterone mostly)

Endocrine regulation of male repro function is very different from that of the female. Why?

The male doesn't develop a surge center in hypothalamus

GnRH occurs in frequent intermittent bursts

Concentrations of FSH are lower but pulses are longer than LH because of secretion of inhibin by testes

LH pulses are closely followed by pulses of Testosterone

Why is pulsatile LH important?`

High interstitial concentrations of testosterone are essential to spermatogenesis, but not constantly needed

Leydig cells may become refractory to high levels of LH

Refractory=unresponsive, thus pulses will maintain a constant hormone supply

Why is pulsatile Testosterone important?

An increase in testosterone leads to decreased FSH over time due to negative feedback on the anterior pituitary.

However Sertoli cells need FSH to function properly, pulsing removes the negative feedback so Sertoli cells continue to function properly.

Testosterone can do 2 things, what are they?

Cross basement membrane and diffuse into Sertoli cells to be converted into both dihydrotestosterone(DHT) and estradiol 17B.

Provide a negative feedback on the hypothalamus through vasculature

The 2 cells of the testis are similar to follicle cells; what are they?

Leydig=Similar to Theca interna cells

Sertoli=Similar to Granulosal cells

Besides Testosterone what do the Testis produce? What affect does this have on the Hypotalamus?

Testis also produce estradiol and other estrogens

They have a negative feedback effect on the hypothalamus

Where does Spermatogenesis take place?

Spermatogenesis takes place in the Seminiterous Tubules

Spermatogenesis consists of 3 phases, what are they?

Proliferation

Meiosis

Differentiation

Proliferation of spermatogenesis

Mitotic divisions involving proliferation and maintenance of spermatogonia

Meiosis of Spermatogenesis

spermocytes give rise to spermatids

Differentiation of Spermatogenesis

Morphological transformation of spherical spermatids into fully differentiated, highly specialized spermatozoa

There are 3 types of spermatogonia, what are they?

A-Spermatogonia A1-A4

I-Spermatogonia

B-Spermatogonia

How is spermatogenesis different for oogenesis?

A constant supply of sperm is always present

There is a constant supply of stem cells that divide mitotically to provide a continual supply of A-spermatogonia

Therefore spermatogenesis continues indefinitely

How are developing germ cells connected?

Germ cells are interconnected by intracellular bridges.

Spermatogonia are only found in basal component of the seminiferous tubule, sperm mature as they move to the lumen

Differentiation

Marked by development of the flagellum and mitochondrial helix

4 Phases of differentiation

Golgi phase

Cap phase

Acrosomal phase

Maturation phase

Golgi Phase

Spermatid contain a large highly developed golgi apparatus

proacrosomic granules form from golgi apparatus

these granules fuse to form the acrosomic vesicle that contains a dense, acrosomal granule.

Centrioles migrate from the cytoplasm to the base of the nucleus

Proximal centrioles give rise to the implantaion apparatus, distal to the axenome.

Cap Phase

Acrosome forms distinct easily recognized cap over the anterior portion of the nucleus.

Acrosomal Phase

Nucleus and cytoplasm continue to spread until it covers about 2/3 of the anteior nucleus

Mitochondria appear

Maturation Phase

Mitochondria assemble around flagellum and assmble in a helical fashion

Spermiation

Sperm released from Sertoli Cells into lumen of seminiferous tubules

What is the structure of a spermatozoa composed of?

Spermatozoa is composed of a head and a tail

Head of spermatozoa

nucleus +acrosome+post nuclear cap

Different for each species

Composed of Apical ridge, acrosome, plasma membrane, postnuclear cap, nuclear ring or equatorial segment, nucleus

Tail of Spermatozoa

Middle Piece+principle piece+terminal piece

Composed of Capitulum, Middle Piece, Principle Piece, Terminal Piece

Spermatogenic Waves

The Mechanism involved in continuous production of sperm is a very difficult process to comprehend

Describe cycle of seminiferous epithelium

The progression through a complete series of cellular associations(stages) at one location along the seminiferous tubule.

Duration of the cycyle of the seminiferous epithelium- time required for this cycle

Stages of the cycle are arbitrarily defined cellular associations which disappear and reappear at predictable intervals

Scientists have looked at a bunch of seminiferous tubules to determine this 8-14 stages

Spermatogenic waves

Distribution of stages along the length of seminiferous tubule at any given instance in time

Two types of sperm transport are

Rapid- Sperm transported in minutes-non-viable

Sustained- sperm transported to oviducts in a trickle like fashion from sperm reservoirs in cervix, uterus and UTJ

General types of metabolism of sperm

Catabolic-sperm DNA is inactive-breakdown of substrates into chemical energy

Anabolic-sperm are not anabolic-formation of compounds from substrates

About this deck

By: Cassie Sell
Created: 2010-12-12
Size: 32 flashcards
Views: 5

About StudyBlue

“I have used this website for three exams, and I see a huge difference in my test results.”
Naj