Functions and Differences of Ovaries in Animals vs. Humans
Human Ovary
The ovary is a female reproductive organ that contains an egg called an ovum. This travels down the fallopian tube further into the uterus after being released, where it could be fertilized by sperm. On either side of the body, there is an ovary (from Latin ovarium 'egg, nut'). Hormones that play a part in the menstrual cycle and fertility are also secreted by the ovaries. Beginning in the prenatal phase and continuing into menopause, the ovary goes through a number of stages. Because of the hormones it metabolizes, it is often classified as an endocrine gland.
[Image will be uploaded soon]
Ovary Structure:
The female gonads are called the ovaries. Each (parts of ovary) ovary is whitish in color and is found in the ovarian fossa, which runs alongside the uterus's lateral wall. The ovarian fossa seems to be the region in front of the ureter and the internal iliac artery which is surrounded by the external iliac artery. The scale of this region is approximately 4 cm x 3 cm x 2 cm. Ovary structure reveals that a capsule surrounds the ovaries, which have an outer cortex and an inner medulla. The tunica albuginea is a capsule made up of dense connective tissue.
Each menstrual cycle, ovulation occurs in one of the two ovaries, which releases an egg.
The infundibulopelvic ligament connects the part of the ovary nearest to the fallopian tube to the tube, and the ovarian ligament connects the other side of the ovary to the uterus.
The hilum is one of the ovaries' other structures and tissues.
Structure of Ovary in Human:-
Ligaments: The section of ovary shows that ovaries are located inside the peritoneal cavity, on either side of the uterus, and are connected by a fibrous cord known as the ovarian ligament. The ovaries are exposed in the peritoneal cavity, but they are attached to the body wall by the ovary's suspensory ligament, which seems to be a posterior extension of the uterus' broad ligament. The mesovarium is the portion of the uterus's thick ligament that protects the ovary.
Parts of the fallopian tube, ovarian ligament, mesovarium, and ovarian blood vessels make up the ovarian pedicle.
Microanatomy: The germinal epithelium is a membrane that covers the top of the ovaries and is made up of simple cuboidal-to-columnar shaped mesothelium. The internal structure of ovary
states that the ovarian cortex is the outer layer, which is made up of ovarian follicles and stroma in between. The cumulus oophorus, membrana granulosa (and the granulosa cells within it), zona pellucida, corona radiata, and primary oocyte are all found in the follicles. The follicle frequently contains the theca of follicle, antrum, and liquor folliculi.
The ovarian medulla is the inner lining. The cortex and medulla are difficult to differentiate, but follicles are rarely located in the medulla.
Follicular cells are flat epithelial cells which arise from the ovary's surface epithelium. Granulosa cells which have modified from flat to cuboidal and proliferate to form a stratified epithelium surround them.
Blood vessels and lymphatics are also found in the ovary.
Function:
When a child reaches puberty, the ovary starts to secrete more hormones. In response to the hormones, secondary sex traits emerge. Starting at puberty, the ovary's structure and role change. Because the ovaries have the ability to control hormones, these are crucial in pregnancy and fertility. A number of feedback mechanisms activate the endocrine system once egg cells (oocytes) are extracted from the Fallopian tube, causing hormone levels to shift. The hypothalamus and pituitary gland are in control of these feedback mechanisms. The hypothalamus sends messages to the pituitary gland.
The pituitary gland, in addition, releases hormones into the ovaries. The ovaries respond by releasing their own hormones in response to this signaling.
Gamete Production:
The ovaries are where egg cells, or female gametes, are produced and released on a regular basis. The immature egg cells (or oocytes) mature in the fluid-filled follicles of the ovaries. Only a single oocyte matures at a time in most cases, but others may mature at the same time.
Follicles are made up of various types and numbers of cells depending on their maturation stage, and their size reflects the stage of oocyte growth.
When the oocyte has completed its maturation in the ovary, the pituitary gland secretes luteinizing hormone, which induces the oocyte's release by follicle rupture, a process known as ovulation.
Hormone Secretion:
Estrogen, inhibin, androgen, and progestogen are all secreted by mature ovaries. The ovaries contain 50% of testosterone in women until menopause, which is then released straight into the blood. The remaining 50% of testosterone in the blood comes from other areas of the body converting adrenal pre-androgens (DHEA and androstenedione) to testosterone.
Estrogen is responsible for the development of secondary sex characteristics in females during puberty, as well as the maturation and maintenance of fully functioning reproductive organs.
Ovarian Aging:
Menopause occurs when a woman's reproductive performance declines as she ages. A decrease in the number of ovarian follicles is linked to this decline. While the human ovary contains approximately 1 million oocytes at birth, just around 500 (about 0.05 percent) of these oocytes ovulate, and the remaining are destroyed. The reduction in ovarian reserve tends to happen at a steady rate with age, with close to complete depletion of the reserve occurring around the age of 52. Pregnancy failure and meiotic errors, which result in chromosomally irregular pregnancies, rise as ovarian reserve and fertility decline with age.
About the age of 20–30, ovarian reserve and fertility are at their peak. The menstrual cycle starts to shift about the age of 45, and the follicle pool tends to shrink dramatically. The events that cause ovarian aging are unknown. Environmental factors, lifestyle patterns, and genetic factors all play a role in aging variability.
Ovary - Animal and Human:
Only one ovary (the left) is functional in birds, with the other remaining vestigial. Female ovaries are similar to male testes in which they are both gonads as well as endocrine glands. Many species that use sexual reproduction, such as invertebrates, have ovaries of some sort in their female reproductive system. They may not, however, evolve in most invertebrates in the same way as they do in vertebrates, and they are not completely homologous.
The presence of tunica albuginea, follicular cells, and other characteristics present in human ovaries are identified in all vertebrates. Many animals, however, release much more eggs during their lifespan than humans, however in fish and amphibians, there could be hundreds, if not millions, of fertile eggs in the ovary at a certain given time. Fresh eggs can grow from the germinal epithelium in these species during their lives. Just mammals as well as some elasmobranch fish have corpora lutea; in many other animals, the remains of the follicle are easily resorbed by the ovary. The egg is fairly large in reptiles, birds, and monotremes, occupying the follicle and distorting the form of the ovary at maturity.
The ovarian medulla is absent in amphibians and reptiles, and the central part of the ovary seems to be a hollow space filled with lymph.
Teleosts' ovaries are hollow as well, but the eggs are shed into the cavity, which then extends into the oviduct. Philometra nematodes are parasitic throughout the ovary of marine fishes and therefore can grow to be very large, with females as large as 40 cm coiled throughout the ovary of a fish half that size. While most normal female vertebrates possess two ovaries, not that all species have them.
The right ovary rarely grows up in most birds and platypuses, therefore only the left is functional. (The kiwi and some, but not all, raptors are exceptions, since they retain both ovaries.) Only the right ovary grows completely in some elasmobranchs. There is only one ovary in jawless fish and some teleosts, which is created by the unification of the paired organs within the embryo.
FAQs on Ovary of Animal and Human: Complete Guide
1. What are the human ovaries and where are they located in the body?
The ovaries are the primary female reproductive organs in humans. A female has two ovaries, which are small, almond-shaped glands located in the lower abdomen, one on each side of the uterus. They are connected to the uterus by ligaments and are situated close to the fallopian tubes.
2. What are the two primary functions of the ovaries in humans and other mammals?
The ovaries have two main functions that are essential for reproduction and female physiology:
Gametogenesis: This is the process of producing and maturing the female gametes, known as ova (eggs). This process is called oogenesis. Each month, one ovary typically releases a mature egg during ovulation.
Endocrine Function: They produce and secrete the primary female sex hormones, mainly estrogen and progesterone. These hormones regulate the menstrual cycle, support pregnancy, and are responsible for the development of female secondary sexual characteristics.
3. Can you describe the internal structure of a human ovary?
The internal structure of a human ovary is complex and divided into two main regions:
The Cortex: This is the outer, functional part of the ovary. It is dense and contains the ovarian follicles. Each follicle contains an oocyte (immature egg) at different stages of development, from primordial follicles to a mature Graafian follicle.
The Medulla: This is the central core of the ovary. It is composed of connective tissue, blood vessels, nerves, and lymphatic vessels that support the cortex.
The entire ovary is covered by a layer of simple cuboidal cells called the germinal epithelium.
4. How does an ovary differ from an ovum?
It is a common point of confusion, but an ovary and an ovum are fundamentally different. The ovary is a complete reproductive organ—a complex structure made of various tissues that produces hormones and eggs. In contrast, an ovum (or egg) is a single, microscopic reproductive cell (a gamete) that is produced inside the ovary. Essentially, the ovary is the organ, and the ovum is the cell it produces for fertilization.
5. Why are the ovaries considered both reproductive and endocrine glands?
The ovaries are considered dual-function glands because they perform tasks for two different body systems:
Reproductive (Exocrine) Gland: Their exocrine function is to produce and release ova (eggs) into the fallopian tube. An exocrine gland secretes its product through a duct or into a specific location, which in this case is the reproductive tract.
Endocrine Gland: Their endocrine function is to secrete hormones like estrogen and progesterone directly into the bloodstream. These hormones travel throughout the body to target other organs and regulate processes like the menstrual cycle and pregnancy, which is the defining characteristic of an endocrine gland.
6. Do all female animals have two ovaries?
While most female vertebrates, including humans and other mammals, have a pair of functional ovaries, this is not universal across the animal kingdom. For example, in most species of birds, only the left ovary and oviduct develop fully and become functional. This is considered an evolutionary adaptation to reduce body weight for flight. Therefore, having two ovaries is common but not a rule for all female animals.
7. What happens to the ovaries after menopause?
After menopause, the primary functions of the ovaries cease. The store of ovarian follicles becomes depleted, which means the ovaries no longer release eggs (ovulation stops). Consequently, the production of estrogen and progesterone dramatically decreases. This hormonal decline leads to the end of menstrual cycles. The ovaries themselves gradually decrease in size and become less active.
8. What are some factors that can affect the health and function of the ovaries?
Several factors can influence the health and proper functioning of the ovaries. These include:
Hormonal Disorders: Conditions such as Polycystic Ovary Syndrome (PCOS) can disrupt the normal hormonal balance and interfere with ovulation.
Age: Ovarian function and egg quality naturally decline as a woman ages, eventually leading to menopause.
Diseases and Conditions: Endometriosis, pelvic inflammatory disease, and ovarian cysts or tumours can physically damage the ovaries or block the fallopian tubes.
Lifestyle Factors: Chronic stress, poor nutrition, smoking, and being significantly overweight or underweight can negatively impact hormonal regulation and ovarian function.
