<< Chapter < Page Chapter >> Page >

Folliculogenesis

Again, ovarian follicles are oocytes and their supporting cells. They grow and develop in a process called folliculogenesis    , which typically leads to ovulation of one follicle approximately every 28 days, along with death to multiple other follicles. The death of ovarian follicles is called atresia, and can occur at any point during follicular development. Recall that, a female infant at birth will have one to two million oocytes within her ovarian follicles, and that this number declines throughout life until menopause, when no follicles remain. As you’ll see next, follicles progress from primordial, to primary, to secondary and tertiary stages prior to ovulation—with the oocyte inside the follicle remaining as a primary oocyte until right before ovulation.

Folliculogenesis begins with follicles in a resting state. These small primordial follicles    are present in newborn females and are the prevailing follicle type in the adult ovary ( [link] ). Primordial follicles have only a single flat layer of support cells, called granulosa cells    , that surround the oocyte, and they can stay in this resting state for years—some until right before menopause.

After puberty, a few primordial follicles will respond to a recruitment signal each day, and will join a pool of immature growing follicles called primary follicles    . Primary follicles start with a single layer of granulosa cells, but the granulosa cells then become active and transition from a flat or squamous shape to a rounded, cuboidal shape as they increase in size and proliferate. As the granulosa cells divide, the follicles—now called secondary follicles    (see [link] )—increase in diameter, adding a new outer layer of connective tissue, blood vessels, and theca cells    —cells that work with the granulosa cells to produce estrogens.

Within the growing secondary follicle, the primary oocyte now secretes a thin acellular membrane called the zona pellucida that will play a critical role in fertilization. A thick fluid, called follicular fluid, that has formed between the granulosa cells also begins to collect into one large pool, or antrum    . Follicles in which the antrum has become large and fully formed are considered tertiary follicles    (or antral follicles). Several follicles reach the tertiary stage at the same time, and most of these will undergo atresia. The one that does not die will continue to grow and develop until ovulation, when it will expel its secondary oocyte surrounded by several layers of granulosa cells from the ovary. Keep in mind that most follicles don’t make it to this point. In fact, roughly 99 percent of the follicles in the ovary will undergo atresia, which can occur at any stage of folliculogenesis.

Folliculogenesis

This multipart figure shows how follicles are generated. The top panel shows the six stages of folliculogenesis. In each stage, the major cell types are labeled. The bottom part shows a micrograph of a secondary follicle and the major parts are labeled.
(a) The maturation of a follicle is shown in a clockwise direction proceeding from the primordial follicles. FSH stimulates the growth of a tertiary follicle, and LH stimulates the production of estrogen by granulosa and theca cells. Once the follicle is mature, it ruptures and releases the oocyte. Cells remaining in the follicle then develop into the corpus luteum. (b) In this electron micrograph of a secondary follicle, the oocyte, theca cells (thecae folliculi), and developing antrum are clearly visible. EM × 1100. (Micrograph provided by the Regents of University of Michigan Medical School © 2012)

Questions & Answers

what is Anatomy
Hannah Reply
because she's not yet at term
Nansi Reply
what is physiology?
Grace Reply
what is physiology
David
Physiology is the study of the functions of the human body
Hannah
am a new one!!
sekela
Name three reasons to study anatomy and physiology
Hills Reply
Why do we need to study anatomy and physiology
Hills Reply
I want to study human anatomy
Ibrahim
What is anatomy
Christabel Reply
anatomy is the branch of medicine in which we study structure and part of the body
Ansar
The art of studying the different parts of any organized body, to discover their situation, structure, and economy; dissection.
ChristMas
anatomy is the study of structures that make up the body and how they re realated to each other
BRIAN
Anatomy is the study of structures of the body and shape of the body and body parts and their relationship to one another.
Abubakar
what is the importance of anatomy
Emeria Reply
cockroch ka sir katne ke bad o jinda kyu rahta
Anil
it helps us to understand the function of human metabolic system and also who these systems works which system play what role and so on
Nouman
It's help us to know the structure, functions and relationship of the human body
Nansi
it helps us to appreciate how the internal structures works
Damilola
Anatomy opens up to us the structures of the various parts of the human body and correlates them to their specific function respectively
Michael
Anatomy is helps us understand and explore much about human structures
Chuks
systemic anatomy in short
Puja Reply
systemic circulation is the circulation in which heart supplies oxygenated blood to cells of body and takes deoxygenated blood away from body to heart
Ajeet
really?
Puja
yeah
BRIAN
ha ji
Ajeet
well much setisfy
Nouman
hello
Limpo
am new here
Limpo
ok
Emeria
am new here
Sindazi
I'm new as well
Crystal
who ask the question about cockroach cutting head
Nouman
the answer is They have an open circulatory system, which there's much less pressure in.After you cut their heads off very often their necks would seal off just by clotting," he adds. "There's no uncontrolled bleeding.The hardy vermin breathe through spiracles, or little holes in each body se
Nouman
does this platform helpful
Sindazi
well it's up-to you how you utilities this
Nouman
thnx ajeet
Puja
hello
AKARAJ
plz anatoy write note
AKARAJ
I think it is helpful
Alfred
Hi
Christabel
hi
Sachin
how do plateletes function in blood clotting
lydia
what are the function of the cell membrane
Elias Reply
the cell membrane helps in allowing and removing substances from the cell. it also aid in protecting the cell and giving it a definite shape.
veezy
The cell membrane is made up of a semipermeable lipid bi-layer which helps to regulate the kind of materials that enters it through active transport and passive diffusion.
Michael
properties of cardiac muscle
hotlan Reply
Myogenic,contain intercalated disc,control involuntary,fond in the heart walls only
AMOS
The exclusive characteristics of heart muscle is consists of Intercalated disc.
Doctor
Among the involuntary muscles only cardiac muscle is Myogenic but rest of involuntary muscles is Neurogenic.
Doctor
What about the exclusive characteristics of smooth muscle apart from lacking myofibrils in it's structure?
AMOS
What is the different between neurogenic and carcinogenic?
AMOS
distinguish between anatomy and physiology
Jonah Reply
Anatomy is the study of body parts and were they are found, physiology is the study of body parts and their functions
Alex
Anatomy is the scientific study of the body structure. While Physiology is the scientific study of the body function
Ossy
Anatomy is te scientic study of body parts and their physical relationship between different systems while physiology is te study of how all body systems works.
AMOS
1, molecules 2, cells 3, organ 4, tissue 5, organ systems 6l, organisms
hamisu Reply
hi
Musaffa
i m new here
Musaffa
hii
Coolx
hi
mushahid
how are you all
mushahid
Am fine bro and you
Nyier
Fine us all
AMOS
smallest part in anatomy
Mood Reply
functions of respiratory system
Dorice Reply
2. If the respiratory rate increases, carbon dioxide is removed from the blood, what effect would this have on blood hydrogen ion levels?
cris Reply
_____________are cells from fibrils and are active in the repair of tissue.
cris

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play




Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Anatomy & Physiology' conversation and receive update notifications?

Ask