[2] Mammalian oogenesis

there is the absence of the ___ in the matured ovary since they have been transformed into ___ and arrested at ___ stage of meiosis

oogonia; oocytes; diplotene

The mammalian oocytes are always associated with concentric layers of cells and together, they constitute the so-called ___

ovarian follicle

Other cells are in different stages of natural degeneration called ___. They present various forms and are named accordingly. The most complex, usually the largest and multilayered, is the matured ovum called the ___

atresia; Graafian Follicle

a layer of simple cuboidal epithelium covering the ovary

germinal epithelium

Germinal Epithelium – a layer of ___ covering the ovary

simple cuboidal epithelium

thick layer of connective tissue beneath the germinal epithelium.

tunica albuginea

Tunica Albuginea – thick layer of connective tissue beneath the ___

germinal epithelium

outer peripheral region of the ovary containing the smaller oogenic cells.

oogonia

inner central region of the ovary where cells are larger and with an abundant stroma

medulla

• region of connective tissues which surround and embed the cells.

• Blood vessels and nerves may be seen along with them especially in the medulla.

stroma

clusters of small rounded cells just beneath the tunica albuginea.They are separated from other clusters of cells by a small amount of stroma

primordial follicle

primordial follicle is composed of two cell types:

• primary oocyte

• follicular cells

large central cell with an eccentric nucleus, i.e., at the periphery and one or two large nucleoli. The cytoplasm is stained lighter than the nucleus

primary oocyte

a single layer of flattened cells around the oocyte. They are spindle shaped and have elongated nuclei.

follicular cells

follicular cells are also called ____

granulosa cells

composed of an enlarged oocyte and a single layer of follicle cells that are cuboidal in shape. They are found between the primordial follicles and other growing follicles.

primary follicle

primary follicle is also called a ____

unilaminar primary follicle

composed of oocyte and three to five layers of follicle cells.

secondary follicle

two types of secondary follicles:

• multilaminar follicle

• antral follicle

composed of oocyte and several layers of follicle cells that proliferate by mitosis. The stratified granulosa cells are cuboidal and tightly packed

multilaminar follicle

multilaminar follicle: In some secondary follicles, the boundary between the oocyte and the follicle cells is marked by an amorphous material, basophilic or otherwise called the ___. It is a glycoprotein synthesized by the ___ and the ___

Zona pellucida; oocyte; follicle cells

so-called due to the presence of a small cavity between the cells which coalesce to form a bigger one called the antrum. The oocyte at this point starts to be displaced towards the periphery as the cavity enlarges and the granulosa cells reorganize.

antral follicle

antral follicle: so-called due to the presence of a small cavity between the cells which coalesce to form a bigger one called the ___. The oocyte at this point starts to be displaced towards the ____ as the cavity enlarges and the granulosa cells reorganize.

antrum; periphery

the matured oocyte surrounded by several layers of follicle cells

graafian follicle

graafian follicle is composed of:

• oocyte

• zona pellucida

• corona radiata

• cumulus oophorus

• antrum

• membrana granulosa

• theca interna

• theca externa

central cell with large cytoplasm and a nucleus surrounded by cells and the antrum.

oocyte

a thick layer of glycoprotein immediately surrounding the oocyte. It may be stained blue or pink with H and E preparation

zona pellucida

2 to 3 layers of granulosa cells outer to zona pellucida. Some of these cells are ovulated together with the oocyte.

corona radiata

a small hillock of cells concentrated on the “lower” region of the oocyte.

cumulus oophorus

a large cavity containing a fluid, liquor folliculi, rich in glycoproteins and steroids secreted by the follicle cells.

antrum

antrum: a large cavity containing a fluid, ___, rich in glycoproteins and steroids secreted by the follicle cells.

liquor folliculi

several layers of columnar cells that enclosed the oocyte and the antrum. These cells are tightly packed and beneath them is the basement membrane which appears as a thin ring around the cells.

membrana granulosa

two to three layers of small lightly stained cells with prominent nucleoli. They synthesize androstenedione which is converted into estrogen by the granulosa cells.

theca interna

theca interna: two to three layers of small lightly stained cells with prominent nucleoli. They synthesize ___ which is converted into ___ by the granulosa cells.

androstenedione; estrogen

several layers of elongated fibroblast cells

theca externa

Both theca interna and externa differentiate from the ___ of the stroma and connective tissue. Together, these two layers constitute the ___

fibroblasts; theca folliculi.

ovarian follicles in different stages of development that undergo a natural process of cell death called atresia. The granulosa cells are detached from the basement membrane, disorganized and the oocyte may be seen free in the antrum.

atretic follicle

atretic follicle: ovarian follicles in different stages of development that undergo a natural process of cell death called ___. The granulosa cells are detached from the ____, disorganized and the oocyte may be seen free in the ____.

atresia; basement membrane; antrum

simply a folded Graafian follicle without the oocyte. The release of the oocyte and liquor folliculi leads to the collapse of the follicular wall.

corpus luteum or yellow body

layer of cells which make up the corpus luteum

• granulosa lutein cells

• theca lutein cells

derived from membrana granulosa which became bigger and lighter staining.

granulosa lutein cells

theca interna cells which became smaller, fewer and basophilic. They occupy the folds of the walls of the corpus luteum

theca lutein cells

The corpus luteum (CL) is an ephemeral endocrine gland that synthesizes ___ and ___. ___ corpus luteum has bigger cells and smaller central cavity while a ___ CL has more abundant fibers than cells.

progesterone; estrogen; Active; regressing

consists of dense connective tissue, mostly collagen, that accounts for its white appearance. The remaining cells are phagocytosed by macrophages.

corpus albicans or white bodies

mammalian oogenesis has two processes:

• development of oocyte

• development of follicle

devt. of oocyte: ___ in the yolk sac migrate toward the ___ that develops into the ___

primordial germ cells; gonadal ridge; ovaries

devt. of oocytes: primordial germ cells divide through ___

mitosis

product after mitosis of primordial germ cells

oogonia

the oogonia transforms into the ___

primary oocyte

primary oocyte: developing eggs are arrested at ___ of meiosis (___ stage) and will only continue at ___

prophase I; diplotene; puberty

primary oocyte: after puberty, development is arrested again at ___ until egg meets with the sperm and proceeds to ovum

prophase II

primary oocytes develop into ____ and then the ____

secondary oocyte; ovum

ready to accept and share its nuclear material

ovum

ovaries are suspended by a broad ligament called the ____ to the peritoneal cavity

mesovarium

not all ____ will become primary oocytes as some degenerates

oogonia

contains no developing oogenic cells

medulla

basophilic cells stain ____

darker

Small round body located at the periphery of the ovarian cortex

primordial follicle

The primordial follicle is composed of a ___ surrounded by a single layer of ___ that rest on the basal lamina

large primary oocyte; flat follicular cells

A slightly larger round body also located at the periphery of the ovarian cortex

primary follicle

the primary follicle contains a ___ surrounded by a single layer of ___ that rest on a basal lamina

large primary oocyte; cuboidal or columnar follicular cells

A round body larger than the primary follicle and located in the deeper part of the ovarian cortex

growing follicle

Smallest growing follicle contains a ___ surrounded by several layers of ___ that show small spaces that represent the developing ___

primary oocyte; follicular cells; antrum

what are the structures present in a growing follicle

• primary oocyte

• vitelline membrane

• zona pellucida

• corona radiata

• cumulus oophorus

• antrum

• basal lamina

• theca folliculi or capsule

large cell with small centrally located nucleus and situated inside the follicle

primary oocyte

cell membrane that appears as thin dark line that encloses the primary oocyte

vitelline membrane

a homogenous glycoprotein material secreted by the primary oocyte and corona radiata that encloses the vitelline membrane

zona pellucida

single layer of follicular cells that surround the zona pellucida

corona radiata

several layers of follicular cells that lie external to the corona radiata and form a stalk that anchors the primary oocyte to the stratum granulosum

cumulus oophorus

• space or cavity containing liquor folliculi that separates the primary oocyte from the stratum granulosum, except at the area occupied by the cumulus oophorus

• Formed by the rearrangement of follicular cells of the stratum granulosum

antrum

• several layers of follicular cells that form the peripheral wall of the growing follicle

• Outermost layer is overlaid with a basal lamina

stratum granulosum

stratum granulosum cells secrete ____

estrogen

thin homogenous glycoprotein material that forms the outer limit of the ovarian follicle and demarcates the follicle from the theca folliculi or capsule

basal lamina

part of the ovarian stroma that surrounds the basal lamina and forms the capsule of the follicle

theca folliculi

what are the two parts of the theca folliculi or capsule

• theca interna

• theca externa

inner cellular layer made up of cells that secrete androgens

theca interna

outer fibrous layer made up of collagen fibers

theca externa

• Largest follicle in the ovary

• Usually bulges from the ovarian surface in preparation for its eventual rupture during ovulation

• Has the same structure as the growing follicle but is larger

mature follicle

section through part of an immature cat ovary

section through several primordial follicles of an immature cat ovary

section through a cat primary follicle

section through an area of the cortex of a cat ovary containing primordial and primary follicles

section through a cat secondary follicle

section through an area of a mature cat ovary

section through a cat graafian follicle

Section through a cat graafian follicle

section through a mature cat ovary

section through a mature cat ovary

section through an adult cat ovary with corpus luteum

ovary of a pregnant cat, section through corpora lutea

Mature cat ovary, section through graafian follicle

Mature cat ovary, section through cortex