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Paired ovals, the testes are each approximately 4 to 5 cm in length and are housed within the scrotum (see [link] ). They are surrounded by two distinct layers of protective connective tissue ( [link] ). The outer tunica vaginalis is a serous membrane that has both a parietal and a thin visceral layer. Beneath the tunica vaginalis is the tunica albuginea, a tough, white, dense connective tissue layer covering the testis itself. Not only does the tunica albuginea cover the outside of the testis, it also invaginates to form septa that divide the testis into 300 to 400 structures called lobules. Within the lobules, sperm develop in structures called seminiferous tubules. During the seventh month of the developmental period of a male fetus, each testis moves through the abdominal musculature to descend into the scrotal cavity. This is called the “descent of the testis.” Cryptorchidism is the clinical term used when one or both of the testes fail to descend into the scrotum prior to birth.

Anatomy of the testis

This diagram shows the cross section of the testis.
This sagittal view shows the seminiferous tubules, the site of sperm production. Formed sperm are transferred to the epididymis, where they mature. They leave the epididymis during an ejaculation via the ductus deferens.

The tightly coiled seminiferous tubules    form the bulk of each testis. They are composed of developing sperm cells surrounding a lumen, the hollow center of the tubule, where formed sperm are released into the duct system of the testis. Specifically, from the lumens of the seminiferous tubules, sperm move into the straight tubules (or tubuli recti), and from there into a fine meshwork of tubules called the rete testes. Sperm leave the rete testes, and the testis itself, through the 15 to 20 efferent ductules that cross the tunica albuginea.

Inside the seminiferous tubules are six different cell types. These include supporting cells called sustentacular cells, as well as five types of developing sperm cells called germ cells. Germ cell development progresses from the basement membrane—at the perimeter of the tubule—toward the lumen. Let’s look more closely at these cell types.

Sertoli cells

Surrounding all stages of the developing sperm cells are elongate, branching Sertoli cells    . Sertoli cells are a type of supporting cell called a sustentacular cell, or sustenocyte, that are typically found in epithelial tissue. Sertoli cells secrete signaling molecules that promote sperm production and can control whether germ cells live or die. They extend physically around the germ cells from the peripheral basement membrane of the seminiferous tubules to the lumen. Tight junctions between these sustentacular cells create the blood–testis barrier    , which keeps bloodborne substances from reaching the germ cells and, at the same time, keeps surface antigens on developing germ cells from escaping into the bloodstream and prompting an autoimmune response.

Germ cells

The least mature cells, the spermatogonia    (singular = spermatogonium), line the basement membrane inside the tubule. Spermatogonia are the stem cells of the testis, which means that they are still able to differentiate into a variety of different cell types throughout adulthood. Spermatogonia divide to produce primary and secondary spermatocytes, then spermatids, which finally produce formed sperm. The process that begins with spermatogonia and concludes with the production of sperm is called spermatogenesis    .

Questions & Answers

coronary circulation ?
Juri Reply
Coronary circulation is the circulation of blood in the blood vessels that supply the heart muscle (myocardium). Coronary arteries supply oxygenated blood to the heart muscle, and cardiac veins drain away the blood once it has been deoxygenated. Because the rest of the body.
Riyaz
coronary circulation ,is flow of blood that supplies the heart tissue itself is the coronary circulation. the functional blood supply of the heart,is the shortest circulation in tha body.
Vineeta
what about the easy way to understand action potential
Bright
event of cardiac cycle
Juri Reply
hii
Chandan
whatisanatom
kaso Reply
anatomy is the scientific way of studying the body structure.
cynthia
the branch of science concerned with the bodily structure of humans, animals, and other living organisms, especially as revealed by dissection and the separation of parts.
Noor
what is means by LAPE and HAPE
Noor
guys i've question what occur when homeostasis balance mechanisms lost
cris Reply
Bladder is blank to the small intestine, what is the right directional term for that?
Julaika Reply
When peristaltic movement is correct.
Farid
what tissue that support body organ?
Sabrina Reply
the skeleton
veronica
Skeleton
GEBAH
skeleton
Juwita
skeleton
Farid
skeleton
Priya
skeleton
Emmanuel
skeleton
Noor
skeleton
BILAL
skeleton
hanuman
how many bones are there in the body
hanuman Reply
go uuu
Prasad
206
Prasad
206
Nelago
206
Esmeralda
206
Joey
baby me 360. and human body 206.found bones.....
Sneha
what is a tissue in Anatomy and physiology
Nelago
206 bones
Juwita
what is an example of a molecule that can directly pass through the phospholipid bilayer of the plasma membrane?
Kathy
206
Johara
how many bones are there in the hand and wrist
hanuman
200 tissue
hanuman
answer 206 bones
GEBAH
axial 80 appendicular 126 total bone is 206
Vineeta
wrist bone 8
Vineeta
baby bone 270 he is correct answer
hanuman
Jo carpus wrist bone h
Vineeta
206
Musonda
206 bones in human body.
Farid
What is Heart attack?
Farid
206
Priti
206 all
Sa
All 206
Sa
A heart attack happens when the flow of oxygen-rich blood to a section of heart muscle suddenly becomes blocked and the heart can't get oxygen. If blood flow isn't restored quickly, the section of heart muscle begins to die. Heart attack treatment works best when it's given right after symptoms occu
Riyaz
how can l understand Anatomy quickly?
Agness Reply
you can't!!!! Anatomy is easy but the physiology takes time to understand. Anatomy is simply systems and organs but you must take time to learn physiology to understand how the anatomy works
Rachael
alright.. so how can l at least memorize the information about physiology?
Agness
what name is given to the fluid that is drawn from the villi to the lymphatic vessels
margaret Reply
I think venous
Noor
lymph
Rachael
I also think it's lymph
Akhi
me too I think lymph
Esmeralda
ans Rhythmic contraction
GEBAH
what are the ten (10) rights for drug administration
GEBAH
importance of muscle in the anatomical structures.
Akomeng Reply
it permits the constant level of movement,and gives structure and shape to the body
Priya
what is assimilation
Asiimwe Reply
cellular level organism level chemical level organ system level tissue level organ level
Aleah Reply
, the current topic
Hilya
cellular level
Priya
tissue level
Priya
organ level
Priya
organ systems level
Priya
organism level
Priya
what is anatomy?
Aleah Reply
anatomy is the study of internal parts of body by disecting it.
Shweta
The study of the internal body parts and it's organs are referred as Anatomy.
Adarsh
hey guys am new here?
Annica Reply
undesrtanding the different part of a cell
Jean
***youtu.be/QXT4OVM4vXI this is a great video to help in understanding. It has helped me allot and learned about the distance between atom.
david
sperm cell and egg cell which one have more cell than the other
Urama Reply
sperm cell!
Longvwam
The sperm is _______ to the sternum
Jean
distal
Rachael
posterior
rOx

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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