Ovary: Structure & Folliculogenesis Video Lecture | Biology Class 12 - NEET

0:0:0: the ovaries are a vital part of the
0:0:2: female reproductive system responsible
0:0:4: for producing and storing the eggs that
0:0:7: are necessary for fertilization and
0:0:9: pregnancy
0:0:10: it's commonly known fact that women are
0:0:13: born with all the eggs they will ever
0:0:14: have usually around 1 to 2 million and
0:0:17: these eggs are stored within the ovaries
0:0:20: however there is much more to the
0:0:23: ovaries than just egg production
0:0:25: in this video we will learn about the
0:0:28: structure and location of the ovary
0:0:30: we will also study an important topic
0:0:33: called folliculogenesis which explains
0:0:35: how follicles develop in the ovary
0:0:38: this topic is important for students
0:0:40: preparing for the neet exam
0:0:43: let's understand the ovary starting from
0:0:45: its structure and location in the female
0:0:47: body
0:0:48: as you already know that in females the
0:0:51: ovaries are the primary sex organs right
0:0:54: they are located on each side of the
0:0:57: lower abdomen and each one is about 2 to
0:1:0: 4 centimeters long just like an
0:1:2: unshelled almond
0:1:4: the ovaries are connected to the uterus
0:1:6: by the ovarian ligament
0:1:8: now before taking a closer look into the
0:1:11: ovaries you should know that what
0:1:13: exactly do the ovaries do
0:1:15: well they have two important jobs
0:1:18: firstly they produce female sex hormones
0:1:21: that regulate menstrual cycles breast
0:1:24: development and other changes during
0:1:26: puberty
0:1:28: secondly the ovaries also produce over
0:1:30: or eggs which are released during
0:1:33: ovulation and can potentially be
0:1:35: fertilized by sperm to start a pregnancy
0:1:38: if you are looking to dive deeper into
0:1:40: the functions of the ovary and learn
0:1:42: more about the female reproductive
0:1:44: system then you must check a detailed
0:1:46: document available on the edurev app
0:1:49: where you can learn everything about the
0:1:51: ovary
0:1:52: and if you want to score good you can
0:1:55: also explore notes of other topics of
0:1:57: all the chapters
0:2:0: so now let's talk about the ovarian
0:2:2: structure
0:2:4: first there is the germinal epithelium a
0:2:7: layer of cubicle cells that cover the
0:2:9: ovary this layer is protected by the
0:2:12: visceral peritoneum
0:2:14: and with germinal epithelium ovary is
0:2:16: attached to the abdominal wall
0:2:19: beneath the epithelium you'll find the
0:2:22: Tunica albuginea a layer of connective
0:2:24: tissue that surrounds the ovarian stroma
0:2:28: the ovaries are made up of different
0:2:30: types of cells including the stromal
0:2:32: cells
0:2:33: the stromal cells are present in the
0:2:36: ovarian stroma which is the bulk of the
0:2:38: ovary that is the inner mass of the
0:2:40: ovary and it's divided into two parts
0:2:43: the cortex and the medulla
0:2:45: the medulla is a dense inner layer of
0:2:48: the stroma while the cortex is a less
0:2:50: dense outer layer of the stroma
0:2:53: so this is the overview of the anatomy
0:2:56: of an ovary
0:2:57: so if we look at the cortex region of
0:3:0: ovaries there are little things called
0:3:2: follicles that are growing up
0:3:4: first they start as acids and then they
0:3:7: grow into primary follicles which then
0:3:10: turn into secondary follicles
0:3:12: after that they become tertiary
0:3:14: follicles and eventually they become
0:3:17: fully mature graphene follicles
0:3:19: and finally they turn into something
0:3:22: called corpus luteum which is a yellow
0:3:24: body after which they become Corpus
0:3:26: albicans which is nothing but a white
0:3:29: body and this process of growth of
0:3:31: follicles is called folliculogenesis
0:3:33: about which we will study in few minutes
0:3:37: but before that let's see what is there
0:3:39: in the medulla
0:3:40: deep inside the ovary there's a special
0:3:43: part called the medulla
0:3:45: it's kind of like the core of the ovary
0:3:48: inside the medulla you can find a bunch
0:3:51: of important stuff like blood vessels
0:3:53: connective tissue fibrous sheets
0:3:55: ligaments and even smooth muscles
0:3:59: now let's talk about the Journey of
0:4:1: follicles or the process of
0:4:3: folliculogenesis in the cortex region of
0:4:5: the ovary
0:4:6: as you already know baby girls have
0:4:9: excels even before they are born
0:4:12: but wait they're not really excels yet
0:4:15: they're called gonia cells
0:4:17: when a baby girl is born she already has
0:4:20: a set number of ugonia cells and no more
0:4:23: will be made
0:4:24: these ugonia cells will eventually grow
0:4:27: and develop into excels as the girl
0:4:30: grows up by the process of
0:4:31: folliculogenesis
0:4:33: now let's see how gonia converts into
0:4:36: primary follicles
0:4:38: so the ugonia first starts dividing into
0:4:41: primary oocytes by the process of
0:4:43: mitosis which are like baby egg cells
0:4:47: these primary oocytes are then
0:4:49: surrounded by a special layer of cells
0:4:51: called granulosar cells or follicular
0:4:53: cells
0:4:54: together primary oocyte plus layer of
0:4:58: granulosa cells they form what is called
0:5:0: a primary follicle
0:5:2: however as the baby girl grows up some
0:5:5: of these follicles degenerate and are
0:5:7: lost so by the time she reaches puberty
0:5:10: only 60 000 to 80 000 primary follicles
0:5:14: remain in each ovary
0:5:16: this degenerative process of follicles
0:5:18: is called follicular atresia and such
0:5:21: follicles are known as atritic follicles
0:5:24: but the remaining 60 to 80 000 primary
0:5:27: follicles Are Not Alone
0:5:29: as each primary follicle contains a
0:5:31: primary oocyte which is covered by a
0:5:34: layer of granulosar cells
0:5:36: now it's time for the primary follicle
0:5:39: to grow more
0:5:40: as the follicle continues to grow some
0:5:43: of the takear cells form a layer around
0:5:45: the primary follicle to form the
0:5:47: secondary follicle
0:5:48: but here is something really important
0:5:50: to know even though the follicle is
0:5:52: growing and changing the primary oocyte
0:5:55: inside of it is still the same size and
0:5:58: hasn't grown yet
0:5:59: hence the secondary follicle contains
0:6:2: the primary oocyte only
0:6:4: come to think of the granulosa cells
0:6:7: they are like a little nest for the
0:6:9: primary oocyte
0:6:11: the granulosa cells provide nutrients
0:6:13: and support to help the primary oocyte
0:6:16: grow and mature
0:6:17: these cells help the oocyte grow and
0:6:20: produce a hormone called estrogen
0:6:22: now if we go one step further when a
0:6:25: tertiary follicle is formed from a
0:6:27: secondary follicle and the primary
0:6:29: oocyte inside it is converted into a
0:6:31: secondary oocyte
0:6:33: the tertiary follicle has a fluid-filled
0:6:36: cavity called an Antrim which is filled
0:6:38: with liquor follicularly
0:6:40: the cells in the tertiary follicle
0:6:42: include granulosar cells and to layers
0:6:44: of take our cells an outer layer that is
0:6:47: takea external which is fibrous and an
0:6:49: inner layer called take our internal
0:6:51: which is cellular
0:6:52: during the tertiary stage the granulosa
0:6:55: cells that connect the secondary oocyte
0:6:58: to the Teka antenna are called as
0:7:0: cumulus oophores
0:7:1: the question related to the cumulus
0:7:4: oforis has been asked in the Neath exam
0:7:6: previously hence keep this concept in
0:7:9: mind
0:7:10: now a time comes when a follicle reaches
0:7:12: its completely matured form that is
0:7:14: graphene follicle
0:7:16: so as tertiary follicle nachos a layer
0:7:19: starts forming over the secondary oocyte
0:7:22: and that primary membrane is called
0:7:24: azona pellucida which is formed around
0:7:27: the plasma membrane of the secondary
0:7:29: oocyte
0:7:30: finally the tertiary follicle matches
0:7:33: into a graphene follicle also known as a
0:7:36: mature follicle
0:7:37: this is the follicle that eventually
0:7:39: releases the ovum or egg
0:7:42: and when a secondary oocyte is released
0:7:44: from the ovary this process is called as
0:7:47: ovulation
0:7:48: ovulation occurs due to the rupturing of
0:7:51: the machographian follicle and the
0:7:53: rupturing of the wall of ovary
0:7:55: and when the oocyte is released the
0:7:57: graphene follicle changes into a yellow
0:8:0: body called the corpus luteum
0:8:2: later the yellow body turns into a white
0:8:5: body called the corpus albicans
0:8:8: so this was a complete process of
0:8:10: folliculogenesis
0:8:12: now in each menstrual cycle which is
0:8:15: around 28 days long on average 1X cell
0:8:18: is released by one of the ovaries
0:8:21: these eggs are called secondaryucides
0:8:24: and they are released by each ovary in
0:8:26: turn
0:8:27: you might be wondering how many eggs a
0:8:30: woman produces in her lifetime
0:8:32: well it turns out that over the course
0:8:35: of her reproductive years which usually
0:8:37: lasts from around 40 to 50 years old
0:8:40: sometimes longer a woman will only
0:8:43: produce about 450 eggs in total
0:8:46: that might sound like a lot but when you
0:8:49: consider that a woman releases one egg
0:8:51: per cycle it's really not that many
0:8:54: but the egg isn't the only thing that
0:8:57: the ovary produces
0:8:58: as the egg develops in a structure
0:9:1: called the follicle some of the cells
0:9:3: around it start producing hormones like
0:9:5: estrogen
0:9:7: estrogen is a very important hormone for
0:9:9: the female body and it helps regulate
0:9:12: things like the menstrual cycle bone
0:9:14: health and even mood
0:9:16: so that's the Journey of agonia
0:9:20: we hope that you have understood the
0:9:22: topic
0:9:23: now here is a secret on how you can
0:9:25: study effectively with the edge of app
0:9:28: you can learn with chapter notes watch
0:9:31: video lectures and solve ncrt based McQ
0:9:34: tests of this chapter on edurev
0:9:37: thank you