Ovary - KSU · Classification Of Eggs Based Upon Distribution of Yolk a) Isolecithal or...

• Ovary is the female gonad or sex gland.

• Gonad: an organ that produces gametes; a testis or ovary.

• gametes (sex cells), ovum in females and spermatozoon in males.

The ovary is composed of two parts:

• Outer cortex :

houses the follicels.

• Inner medulla:

is the middle region composed of

connective tissue, blood vessels and

lymphatics.

1Dr. Mu`ath Alghadi, PhD.26-Feb-18

26-Feb-18 Dr. Mu`ath Alghadi, PhD. 3

Folliculogenesis• Pre-antral Phase

• Antral Phase

Unilayer

primary

follicle

Secondary

follicle

Multilayer

primary

follicleEarly Antral Late Antral Preovulatory

• Primordial follicle:• Single layer of flattened follicular squamous cells (granulosa

cells) surrounds the primary oocyte and segregated from it by the basal lamina.

• Primary follicle:• The oocyte growth rapidly and increase in diameter, the

nucleus enlarges and is then called a germinal vesicle, the follicular cells form a single layer of cuboidal cells.

• Secondary (preantral) follicle:• Follicular cells proliferate by mitosis and form stratified

follicular cells (granulosa layer), a thick coat of glycoproteins surrounds the oocytes (Zona pellucida).

• Tertiary (Early antral ) follicle: • The stroma immediately around the follicle differentiate into

two layers; theca interna and theca externa, follicular fluid startto accumulates between the cells inside cavities. These cavitiescoalesce in one large cavity (antrum).

• Mature preovulatory follicle (16-25mm): • Follicular cavity increases in size, and the oocyte adheres to the

wall of the follicle by a small pedicle of cells (cumulusoophorus). The granulosa cells that are close contact with zonapellucida around the ovum become elongated and form thecorona radiate, which accompanies the ovum when it leavesthe ovary.

Ultrastructure of Graafian follicle

• Theca Folliculi (fibrovascular layer)Theca externa

Theca interna

• Membrana GranulosaSeveral layers of granulosal cells

• Antrum contain follicular fluid

• Cumulus oophorusA cluster of cumulus cells that surround the oocyte both in the ovarian follicle and after ovulation

The innermost layer of the cumulus oophorus that directly adjacent to the zona pellucida called corona radiata

• Ovum (secondary oocyte)

Ultrastructure of the ovum

• Corona radiata• Long processes

• Zona pellucida

• Plasma membrane• Microvilli

• Nucleus (Germinal vesicle)

• Nucleolus (Germinal spot)

• Cytoplasm (Ooplasm)ZP

ooplasmPM

Folliculogenesis

TESTIS H&E

SEMINIFEROUS TUBULES

INTERSTITIAL TISSUE

TESTIS H&E

INTERSTITIAL TISSUE

Convoluted portion of tubular compartment

• Two types of cells

A. Somatic cells (Sertoli cells)

B. Germ cells1. Spermatogonium

2. Primary spermatocytes

3. Secondary spermatocytes

4. Spermatids

5. sperm

SEMINIFEROUS

TUBULES

Sertoli cellLeydig cell

Seminiferous tubules26-Feb-18 Dr. Mu`ath Alghadi, PhD. 23

Frog spermatozoon

Total length 0.03 to 0.04 mm.

The mature spermatozoon averages about 0.03 mm. in

length. It has an elongated, solid-staining head (nucleus)

with an anterior acrosome, pointing outwardly toward the

periphery of the seminiferous tubule. The short middle

piece generally is not visible but the tail appears as a gray

filamentous extension into the lumen, about four or moretimes the length of the sperm head.

• Ovaries of the frog are paired, multi-lobed organs, Each lobe of the ovary is hollow and its cavity is continuous with the other 7 to 12 lobes.

• Ovaries are small structures consisting three layers:1. Outer theca external2. Middle germinal epithelium3. Inner theca internal

• From middle germinal epithelium, single epithelium cell enlarges and forms the egg.

• Eggs are formed from the germinal epithelium. They become mature after passing through the following stages:

1. Multiplication phase: Genital epithelium divides into numerous cells called oogonia by mitotic division.

2. Growth phase: After absorbing nutrients, these cells become large which are called primary oocytes.

3. Maturation phase: In the first meiotic cell division each cell is divided into a large secondary oocyte and smaller known as first polar bodies. The first polar bodies disintegrate. The second meiotic division produces the ovum proper and the second polar body.

• The theca interna surrounds each egg except for the limited area bulging toward the body cavity, where it is covered by only the theca externa.

• This is the region which will be ruptured during ovulation to allow the egg to escape its follicle into the body cavity.

• The theca interna, plus the limited covering of the theca externa, and the follicle cells together comprise the ovarian follicle.

Classification Of Eggs Based Upon Amount of Yolk

Egg Type Representative Organisms

a) Alecithal - Almost without yolk. Placental mammals

b) Meiolecithal - Small amount of yolk. Echinoderms, amphioxus, marsupials

c) Mesolecithal - Moderate amount of yolk. Lung-fishes, frogs, and toads.

d) Polylecithal - Very large amounts of yolk. Sharks, bony fishes, reptiles, birds, insects.

3926-Feb-18 Dr. Mu`ath Alghadi, PhD.

Classification Of Eggs Based Upon Distribution of Yolk

a) Isolecithal or Homolecithal - Yolk is evenly distributed. Occurs in the alecithal andmeiolecithal eggs of echinoderms, amphioxus, marsupials, and other mammals.

b) Telotecithal - Yolk is concentrated on one end of the egg, the vegetal hemi-sphere,with the cytoplasm plus the nucleus concentrated the at other end, the animalhemisphere. Occurs in the meiolecithal and polylecithal eggs of frogs, toads, birds,reptiles etc.

c) Centrolecithal - Yolk is in the center of the egg, with cytoplasm around it. Example: Insect eggs

2mm in diameter

Two vitelline membranes bound the egg, which is encircled by albumen.

Unfertilized egg of Xenopus has a polarity along the animal –vegetal axis

Each egg has two colours, white is due to yolk that lies downward and black part is of less weight that lies on the surface of the water. These are also called vegetal and animal pole respectively.

Paired testes in males

SG, SpermatogoniaPS, Primary spermatocyteSs, Secondary spermatocyteMS, Mature spermatocyteL, Lumen

original magnification ×80026-Feb-18 Dr. Mu`ath Alghadi, PhD. 50

Egg production• Most avian species retain only the left ovary, oviduct, and shell gland at hatch

(with exceptions)

• In early stages of embryonic development, each female bird has two ovaries; only the left one develops into a functional organ.

• A mature ovary looks like a cluster of grapes. and may contain up to 4,000 small ova which can develop into mature ova.

• Variation among bird species in the relative amount of yolk in eggs and the amount of energy available to the developing embryo

• Reptiles and birds - ovaries solid but develop irregular, fluid-filled lacunae (cavities); eggs discharged into coelom

• Mammals - ovaries compact; no large chambers or lacunae

• The oviduct opens medially to ovary in a funnel-shaped ostium.

• Ovulation results in the release of an egg from a mature follicle on the surface of the ovary.

• The egg, is picked up by the ostium and ciliary currents carry it into the magnum region. Over about three hours the egg receives a coating of albumen.

• The egg then passes into the isthmus, where the shell membranes are deposited. This takes about one hour.

• The egg them moves to the uterus, or shell gland, where the calcareous shell is added and, in some birds, pigment is added in characteristic patterns.

• The egg then passes into the vagina and cloaca for laying.

• Ovary consist from basophilic cortex, while the medulla is more eosinophilic.

• The ovarian medulla consists of connective tissues, blood vessels, nerves and smooth muscle.

• The ovarian cortex contains a different follicular development stages from primordial follicles, small white follicle, small yellow follicles to large, yellow, yolk-filled pre-ovulatory follicles.

• Large follicles protrude from the surface of the ovary on short stalks while small follicles bulge from the surface.

Five pre-ovulatory follicles are present (F1–F5). Small yellow follicles (SYF) and a regressing post-ovulatory follicle (RF).

• A Ovary with large pre-ovulatory follicles (yellow), small yellow follicles (white), small white follicles (grey)

• B hilus region of ovary where nerves and vessels enter the ovarian medulla

• C Wolffian remnant tissues

• D infundibulum of the oviduct; E magnum of the oviduct; F isthmus of the oviduct; G shell gland; H cloaca.

• The more eosinophilic medulla of the mature laying hen ovary can usually be distinguished from the more basophilic cortex containing the follicles.

This image also includes small white (SWF), primary (PF), primordial (unlabeled), and regressing (RF) follicles. H & E. 40×.

Cuboidal ovarian surface epithelium adjacent to a small white follicle (SWF) and a primordial follicle (Pr). H & E 400×26-Feb-18 Dr. Mu`ath Alghadi, PhD. 62

The simple cuboidal ovarian surface epithelium (OSE) overlying primordial follicles

The image includes a small white follicle (SWF) and a primordial follicle (Pr). A single layer of granulosa cells (GC) delineates each follicle. The small white follicle is also surrounded by theca interna and theca externa layers. Luteal cell clusters (LC) are visible in the theca interna layer. H & E. 400×.26-Feb-18 Dr. Mu`ath Alghadi, PhD. 64

Cleavage is a series of rapid mitotic divisions wherein the enormous volume of zygote cytoplasm is divided into numerous smaller cells called blastomeres, by the end of cleavage, they form a sphere known as a

blastula (blastocyst)

Germinal Period

Morula

Fluid Filled Cavity

Secondary Oocytes

Blastocyst consists of a large number of blastomeres arranged to form a hollow sphere. Group of cells localized inside one pole called inner

cell mass, the surface cells of blastula are trophoblasts where the fluid filled cavity is called a blastocoele.

Hatching Blastocyst

Zona Pellucida

Formation of the blastocyst

Sodium channels appear on the surface of the outer trophoblast cells; sodium and water are pumped into the forming blastocoele.

Early blastocyst Later blastocyst

blastocoele

inner cell mass

Ovary - KSU · Classification Of Eggs Based Upon Distribution of Yolk a) Isolecithal or...

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