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Biology english notes female reproductive system brain origin of life

Biology english notes female reproductive system brain origin of life : The external part of the female reproductive organs is called the vulva, which means covering. Located between the legs, the vulva covers the opening to the vagina and other reproductive organs inside the body.A female’s internal reproductive organs are the vagina, uterus, fallopian tubes, and ovaries.

How does the female reproductive system work?

female reproductive system The fleshy area located just above the top of the vaginal opening is called the mons pubis. Two pairs of skin flaps called the labia (which means lips) surround the vaginal opening. The clitoris, a small sensory organ, is located toward the front of the vulva where the folds of the labia join. Between the labia are openings to the urethra (the canal that carries pee from the bladder to the outside of the body) and vagina. When girls become sexually mature, the outer labia and the mons pubis are covered by pubic hair.

Biology english notes female reproductive system brain origin of life

Female reproductive system | everyday health
Biology English Notes Female Reproductive System Brain Origin Of Life 21

The vagina is a muscular, hollow tube that extends from the vaginal opening to the uterus. Because it has muscular walls, the vagina can expand and contract. This ability to become wider or narrower allows the vagina to accommodate something as slim as a tampon and as wide as a baby. The vagina’s muscular walls are lined with mucous membranes, which keep it protected and moist.

The vagina serves three purposes: female reproductive system

  1. It’s where the penis is inserted during sexual intercourse.
  2. It’s the pathway (the birth canal) through which a baby leaves a woman’s body during childbirth.
  3. It’s the route through which menstrual blood leaves the body during periods.
Female reproductive system
Biology English Notes Female Reproductive System Brain Origin Of Life 22

female reproductive system A very thin piece of skin-like tissue called the hymen partly covers the opening of the vagina. Hymens are often different from female to female. Most women find their hymens have stretched or torn after their first sexual experience, and the hymen may bleed a little (this usually causes little, if any, pain). Some women who have had sex don’t have much of a change in their hymens, though. And some women’s hymens have already stretched even before they have sex.

Reproductive System

The vagina connects with the uterus, or womb, at the cervix (which means neck). The cervix has strong, thick walls. The opening of the cervix is very small (no wider than a straw), which is why a tampon can never get lost inside a girl’s body. During childbirth, the cervix can expand to allow a baby to pass.

female reproductive system The uterus is shaped like an upside-down pear, with a thick lining and muscular walls — in fact, the uterus contains some of the strongest muscles in the female body. These muscles are able to expand and contract to accommodate a growing fetus and then help push the baby out during labor. When a woman isn’t pregnant, the uterus is only about 3 inches (7.5 centimeters) long and 2 inches (5 centimeters) wide.

At the upper corners of the uterus, the fallopian tubes connect the uterus to the ovaries. The ovaries are two oval-shaped organs that lie to the upper right and left of the uterus. They produce, store, and release eggs into the fallopian tubes in the process called ovulation (pronounced: av-yoo-LAY-shun).

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Biology : There are two fallopian (pronounced: fuh-LO-pee-un) tubes, each attached to a side of the uterus. Within each tube is a tiny passageway no wider than a sewing needle. At the other end of each fallopian tube is a fringed area that looks like a funnel. This fringed area wraps around the ovary but doesn’t completely attach to it. When an egg pops out of an ovary, it enters the fallopian tube. Once the egg is in the fallopian tube, tiny hairs in the tube’s lining help push it down the narrow passageway toward the uterus.

The ovaries (pronounced: OH-vuh-reez) are also part of the endocrine system because they produce female sex hormones such as estrogen (pronounced: ESS-truh-jun) and progesterone (pronounced: pro-JESS-tuh-rone).

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Biology How Does the Female Reproductive System Work?

The female reproductive system enables a woman to:

  • produce eggs (ova)
  • have sexual intercourse
  • protect and nourish a fertilized egg until it is fully developed
  • give birth

Sexual reproduction couldn’t happen without the sexual organs called the gonads. Most people think of the gonads as the male testicles. But both sexes have gonads: In females the gonads are the ovaries, which make female gametes (eggs). The male gonads make male gametes (sperm).

When a baby girl is born, her ovaries contain hundreds of thousands of eggs, which remain inactive until puberty begins. At puberty, the pituitary gland (in the central part of the brain) starts making hormones that stimulate the ovaries to make female sex hormones, including estrogen. The secretion of these hormones causes a girl to develop into a sexually mature woman.

Toward the end of puberty, girls begin to release eggs as part of a monthly period called the menstrual cycle. About once a month, during ovulation, an ovary sends a tiny egg into one of the fallopian tubes.

Unless the egg is fertilized by a sperm while in the fallopian tube, the egg leaves the body about 2 weeks later through the uterus — this is menstruation. Blood and tissues from the inner lining of the uterus combine to form the menstrual flow, which in most girls lasts from 3 to 5 days. A girl’s first period is called menarche (pronounced: MEH-nar-kee).

It’s common for women and girls to have some discomfort in the days leading to their periods. Premenstrual syndrome (PMS) includes both physical and emotional symptoms that many girls and women get right before their periods, such as:

  • acne
  • bloating
  • tiredness
  • backaches
  • sore breasts
  • headaches
  • constipation
  • diarrhea
  • food cravings
  • depression
  • irritability
  • trouble concentrating or handling stress

PMS is usually at its worst during the 7 days before a girl’s period starts and disappears after it begins.

Many girls also have belly cramps during the first few days of their periods caused by prostaglandins, chemicals in the body that make the smooth muscle in the uterus contract. These involuntary contractions can be dull or sharp and intense.

It can take up to 2 years from menarche for a girl’s body to develop a regular menstrual cycle. During that time, her body is adjusting to the hormones puberty brings. On average, the monthly cycle for an adult woman is 28 days, but the range is from 23 to 35 days.

What Happens If an Egg Is Fertilized?

If a female and male have sex within several days of the female’s ovulation, fertilization can happen. When the male ejaculates (when semen leaves the penis), a small amount of semen is deposited into the vagina. Millions of sperm are in this small amount of semen, and they “swim” up from the vagina through the cervix and uterus to meet the egg in the fallopian tube. It takes only one sperm to fertilize the egg.

About 5 to 6 days after the sperm fertilizes the egg, the fertilized egg (pronounced: zygote) has become a multicelled blastocyst. A blastocyst (pronounced: BLAS-tuh-sist) is about the size of a pinhead, and it’s a hollow ball of cells with fluid inside. The blastocyst burrows itself into the lining of the uterus, called the endometrium. The hormone estrogen causes the endometrium (pronounced: en-doh-MEE-tree-um) to become thick and rich with blood. Progesterone, another hormone released by the ovaries, keeps the endometrium thick with blood so that the blastocyst can attach to the uterus and absorb nutrients from it. This process is called implantation.

As cells from the blastocyst take in nourishment, another stage of development begins. In the embryonic stage, the inner cells form a flattened circular shape called the embryonic disk, which will develop into a baby. The outer cells become thin membranes that form around the baby. The cells multiply thousands of times and move to new positions to eventually become the embryo (pronounced: EM-bree-oh).

After about 8 weeks, the embryo is about the size of a raspberry, but almost all of its parts — the brain and nerves, the heart and blood, the stomach and intestines, and the muscles and skin — have formed.

During the fetal stage, which lasts from 9 weeks after fertilization to birth, development continues as cells multiply, move, and change. The fetus (pronounced: FEE-tis) floats in amniotic (pronounced: am-nee-AH-tik) fluid inside the amniotic sac. The fetus gets oxygen and nourishment from the mother’s blood via the placenta (pronounced: pluh-SEN-tuh). This disk-like structure sticks to the inner lining of the uterus and connects to the fetus via the umbilical (pronounced: um-BIL-ih-kul) cord. The amniotic fluid and membrane cushion the fetus against bumps and jolts to the mother’s body.

Pregnancy lasts an average of 280 days — about 9 months. When the baby is ready for birth, its head presses on the cervix, which begins to relax and widen to get ready for the baby to pass into and through the vagina. Mucus has formed a plug in the cervix, which now loosesn. It and amniotic fluid come out through the vagina when the mother’s water breaks.

When the contractions of labor begin, the walls of the uterus contract as they are stimulated by the pituitary hormone oxytocin (pronounced: ahk-see-TOE-sin). The contractions cause the cervix to widen and begin to open. After several hours of this widening, the cervix is dilated (opened) enough for the baby to come through. The baby is pushed out of the uterus, through the cervix, and along the birth canal. The baby’s head usually comes first. The umbilical cord comes out with the baby. It’s clamped and cut close to the navel after the baby is delivered.

The last stage of the birth process involves the delivery of the placenta, which at that point is called the afterbirth. After it has separated from the inner lining of the uterus, contractions of the uterus push it out, along with its membranes and fluids.

Biology english notes female reproductive system brain origin of life
Biology English Notes Female Reproductive System Brain Origin Of Life 23
Biology english notes female reproductive system brain origin of life
Biology English Notes Female Reproductive System Brain Origin Of Life 24
Biology english notes female reproductive system brain origin of life
Biology English Notes Female Reproductive System Brain Origin Of Life 25
Picture of human brain biology english notes female reproductive system brain origin of life
Biology English Notes Female Reproductive System Brain Origin Of Life 26

The brain is one of the largest and most complex organs in the human body.
It is made up of more than 100 billion nerves that communicate in trillions of connections called synapses.

The brain is made up of many specialized areas that work together:
• The cortex is the outermost layer of brain cells. Thinking and voluntary movements begin in the cortex.
• The brain stem is between the spinal cord and the rest of the brain. Basic functions like breathing and sleep are controlled here.
• The basal ganglia are a cluster of structures in the center of the brain. The basal ganglia coordinate messages between multiple other brain areas.
• The cerebellum is at the base and the back of the brain. The cerebellum is responsible for coordination and balance.

The brain is also divided into several lobes:
• The frontal lobes are responsible for problem solving and judgment and motor function.
• The parietal lobes manage sensation, handwriting, and body position.
• The temporal lobes are involved with memory and hearing.
• The occipital lobes contain the brain’s visual processing system.

The brain is surrounded by a layer of tissue called the meninges. The skull (cranium) helps protect the brain from injury.

Brain biology english notes female reproductive system brain origin of life
Biology English Notes Female Reproductive System Brain Origin Of Life 27

The Origin of Life

We know how life, once it began, was able to proliferate and diversify until it filled (and in many cases created) every niche on the planet. Yet one of the most obvious big questions—how did life arise from inorganic matter?—remains a great unknown.

Most historians would say that the modern era of experimental research in origin-of-life studies began in a basement laboratory in the chemistry department of the University of Chicago in 1953. Harold Urey, a Nobel laureate in chemistry, and Stanley Miller, then a graduate student, put together a tabletop apparatus designed to look at the kinds of chemical processes that might have occurred on the planet soon after its birth. They showed that organic molecules (in this case amino acids) could be created from inorganic materials by natural environmental conditions such as acidic solution, heat and electrical discharge (lightning), without the mediation of enzymes. This finding triggered a wave of new thinking about both the origin and nature of life. (Today, the consensus is that Miller and Urey had the wrong atmospheric components in their apparatus, so the process they discovered was probably not representative of the emergence of life on Earth. It nevertheless pointed to the potential fecundity and diversity of nonenzymatic primordial chemistry.)

Since 1953, we have found many of the same simple organic molecules in meteorites, comets and even interstellar gas clouds. Far from being special, then, the simplest of the molecules we find in living systems—life’s building blocks—seem to be quite common in nature. To many, the real question was how these basic building blocks got put together into living systems, and, equally important, how the molecules that led to modern life were selected out of the messy molecular milieu in which they arose.

The ubiquity of simple molecules suggested an appealing scenario that had a profound effect on the way investigators approached the origin of life throughout the last half of the 20th century. The scenario went like this: After the Earth cooled enough to allow oceans to form, the Miller-Urey process or something like it produced a rain of organic matter. In a relatively short time, the ocean became a broth of these molecules, and given enough time, the right combination of molecules came together by pure chance to form a replicating entity of some kind that evolved into modern life.

Biology english notes female reproductive system brain origin of life

Scientists called this scenario the Oparin-Haldane conjecture, but it was given a provocative nickname that endures in the popular consciousness—Primordial Soup.

The essential legacy of the Primordial Soup was twofold: It simplified the notion of the origin of life to a single pivotal event, and then it proposed that that event—the step that occurred after the molecules were made—was a result of chance. In the standard language, life is to be seen, in the end, as a “frozen accident.” In this view, many fundamental details about the structure of life are not amenable to explanation. The architecture of life is just one of those things. Although many modern theories are less extreme than this, frozen-accident thinking still influences what some of us ask about the origin of life and how we prioritize our experiments.

RNA World

The next major advance came in the early 1980s, when Thomas Cech and Sidney Altman showed that some RNA molecules can act as enzyme-like catalysts. The frozen-accident argument was then replaced by a suggestive scenario in which something like RNA was assembled by chance, and was then able to fill twin roles as both enzyme and hereditary molecule in the runup to life. The RNA systems were then acted upon by natural selection, leading to greater molecular complexity and, eventually, something like modern life. Whereas most scientists believe, on the basis of Cech and Altman’s work, that life went through an early RNA-dominated phase (dubbed “RNA World”), the “RNA First” scenario has again a quality of frozen accident. Between prebiological chemistry and RNA World, a large leap occurs, requiring that molecules appear having at least a familial resemblance to the complex molecules in the vials of Cech and Altman, for that is the assumption upon which the relevance of their findings to the origin of life depends.

Wp 16030961286515557270974148622773
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Reproduction:

(1) Reproduction is defined as a biological process in which every living organism give rise to new organisms similar to themselves.(2) Basic features of reproduction:   (i) Replication of DNA   (ii)  Cell division (only mitotic, or both mitotic and meiotic)   (iii) Formation of reproductive bodies or units.   (iv) Development of reproductive bodies into offsprings.

Asexual versus Sexual Reproduction

(1) reproduction is defined as a biological process in which every living organism give rise to new organisms similar to themselves. (2) basic features of reproduction:   (i) replication of dna   (ii)  cell division (only mitotic, or both mitotic and meiotic)   (iii) formation of reproductive bodies or units. (iv) development of reproductive bodies into offsprings.
Biology English Notes Female Reproductive System Brain Origin Of Life 29

Organisms that reproduce through asexual reproduction tend to grow in number exponentially. However, because they rely on mutation for variations in their DNA, all members of the species have similar vulnerabilities. Organisms that reproduce sexually yield a smaller number of offspring, but the large amount of variation in their genes makes them less susceptible to disease.

Many organisms can reproduce sexually as well as asexually. Aphids, slime molds, sea anemones, and some species of starfish are examples of animal species with this ability. When environmental factors are favorable, asexual reproduction is employed to exploit suitable conditions for survival, such as an abundant food supply, adequate shelter, favorable climate, disease, optimum pH, or a proper mix of other lifestyle requirements. Populations of these organisms increase exponentially via asexual reproductive strategies to take full advantage of the rich supply resources. When food sources have been depleted, the climate becomes hostile, or individual survival is jeopardized by some other adverse change in living conditions, these organisms switch to sexual forms of reproduction.

Sexual reproduction ensures a mixing of the gene pool of the species. The variations found in offspring of sexual reproduction allow some individuals to be better suited for survival and provide a mechanism for selective adaptation to occur. In addition, sexual reproduction usually results in the formation of a life stage that is able to endure the conditions that threaten the offspring of an asexual parent. Thus, seeds, spores, eggs, pupae, cysts, or other “over-wintering” stages of sexual reproduction ensure the survival during unfavorable times as the organism can “wait out” adverse situations until a swing back to suitability occurs.

Types of Sexual and Asexual Reproduction

Asexual and sexual reproduction, two methods of reproduction among animals, produce offspring that are clones or genetically unique.

Types of sexual and asexual reproduction
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