Histology of the ovary

The layers of cells/tissues of the ovary include:

Germinal Epithelium. This simple squamous or low cuboidal-type epithelium covers the free surface of the ovary.

Tunica Albuginea. This dense connective tissue beneath the germinal epithelium supports the structure of the ovary.

Cortex. This outer connective tissue of the ovary contains follicles.

Medulla. This inner connective tissue is highly vascularized and innervated, but lacks follicles except in equids.

Follicles. These structures within the ovary contain an ovum and cells responsible for steroidogenesis, which develop through the following stages:

Primary follicles: spheroidal primary oocytes about 45 mm in diameter surrounded by a single layer of follicle cells that separate the oocyte from adjacent interstitial tissue. Secondary and tertiary follicles: growing follicles with multiple layers of cells from differentiation of follicle cells into granulosa cells surrounding the ovum; increased size of the oocyte nucleus and mitochondria; formation of the zona pellucida around the primary oocyte; and development of an antrum in tertiary follicles. Mature Graafian follicles: These large, blister-like structures have an antrum filled with follicular fluid; theca interna and theca externa layers; prominent cumulus oophorus and corona radiata cells attached to the ovum; and the zona pellucida surrounding the vitelline

Primary Oocyte

Germinal Epithelium

Primary Follicle

Cumulus

Oophorus Graafjan Follicle

Primary Oocyte

Cumulus

Oophorus Graafjan Follicle

Germinal Epithelium

Primary Follicle

Corpus

Hemorrhagicum

Corpus Luteum

Fig. 2 Schematic illustration of the ovary showing the primary structures and their sequence of development during the ovarian cycle.

Corpus

Hemorrhagicum

Corpus Luteum

Fig. 2 Schematic illustration of the ovary showing the primary structures and their sequence of development during the ovarian cycle.

Endometrium

Artery

Myometrium Perimetrium

Stratum spongiosum

Inner circular muscle

Outer _ longitudinal muscle

Vein

Fig. 3 Schematic illustration of the uterine wall of domestic animals. (View this art in color at www.dekker.com.)

Stratum spongiosum

Inner circular muscle

Outer _ longitudinal muscle

Endometrium

Artery

Myometrium Perimetrium

Vein

Fig. 3 Schematic illustration of the uterine wall of domestic animals. (View this art in color at www.dekker.com.)

membrane of the ovum. These follicles produce estrogens that induce an ovulatory surge of luteinizing hormone (LH) for ovulation and release of the ovum into the oviduct. Following ovulation, granulosa and theca cells form transitional structures on the ovary known as: 1) the corpus hemorhhagicum (CH), a newly ruptured follicle containing a blood clot and proliferating granulosa and theca cells; 2) the corpus luteum (CL), with yellow body or solid glandular structure formed through hyperplasia and hypertrophy of granulosa and theca cells (one CL forms from each ovulated follicle to secrete progesterone, the hormone required for pregnancy); and 3) the corpus albicans (CA), the white body or connective tissue remains of the CL that regress due to effects of luteolytic prostaglandin F2a if pregnancy is not established.

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