Human Fertilization, Hormones and Reproduction

Fertilization in Humans

• If semen deposits into the vagina shortly before or after ovulation, fertilization may occur.
• The sperm takes around two or three hours to reach the egg in the fallopian tube.
• Only one sperm penetrates and fertilizes the egg.
• The sperm's nucleus joins the egg's nucleus, forming one cell.

Steps of Fertilization

• Step 1: An egg leaves the ovary and enters the fallopian tube.
• Step 2: Sperm enters the egg and unites with the nucleus
• Step 3: The fertilized egg divides.
• Step 4: Cells attach to the uterus.

Hormones and Ovulation

• The pituitary gland releases follicle-stimulating hormone (FSH) to stimulate follicle development in the ovary.
• Luteinizing hormone (LH) is released by the pituitary gland and causes the maturation and release of eggs from the ovary during ovulation.
• The pituitary is controlled by hormones secreted by the hypothalamus.

Ovaries and Fallopian Tubes

• The ovaries are surrounded by the funnel-like openings of the fallopian tubes.
• An egg released by an ovary enters the fallopian tube.
• Fertilization occurs in the upper part of the fallopian tube.
• If the egg is fertilized, the resulting zygote moves to the uterus and attaches to the uterine walls to develop.
• If the egg that is released is not fertilized, it travels through the uterus and leaves the body via the vagina during the menstrual flow.
• The female body contains two ovaries, which release a mature egg alternately every 28 days.
• Each ovary holds thousands of immature egg cells, but only around 400 will mature and be released during a woman's reproductive life.
• An egg is typically released every 28 days, starting from ages 12-14 until a woman is 45-50 years old.

Hormones and the Reproductive Process

• The immature egg cell develops inside a follicle in the ovary.
• Estrogen, a female hormone, is released which stimulates the lining of the uterus and increases cell division and blood supply to the uterus, which causes tissues to accumulate
• The follicle breaks and releases the egg when it matures.
• The follicle then secretes more estrogen and progesterone.
• These hormones stimulate the thickening of the uterine wall tissues, forming part of the placenta to nourish the developing fetus.

The Human Embryo

• The embryo implants in the uterus, where it grows and is nourished, respires, and has its waste removed via the placenta.
• The embryo is enclosed by a sac called the amnion.
• The amnion is filled with amniotic fluid, this sac and fluid together are commonly called the "bag of water".
• The fluid keeps the embryo moist and protects it from bumps and jolts.
• The placenta connects the mother and the embryo.

The Umbilical Cord

• The umbilical cord connects the embryo and placenta.
• The umbilical cord has blood vessels transporting nourishment to the embryo and removing its wastes.
• The blood vessels of the embryo and the mother stay separate but come close together in the placenta.
• Oxygen and nutrients diffuse from the mother's blood across the placental membranes into the embryo's blood, which also causes wastes and carbon dioxide diffuse across the placental membranes and into the mother's blood .
• Wastes are carried to the mother's lungs and kidneys for elimination.

Final Stages of Pregnancy and Childbirth

• Repeated contractions move the baby slowly toward the vagina.
• The "bag of water," in which the baby has been floating during gestation, breaks and the fluid is released.
• Muscle contractions become more frequent and stronger until the baby is pushed out through the vagina and is born.
• The baby may be blue at first because it has stopped taking oxygen through the umbilical cord.
• The baby turns pink as it takes its first breath and its blood takes up more oxygen.
• A nurse or doctor may need to suction fluid from the baby's nose and mouth.
• The umbilical cord is tied and cut off.
• The small piece of cord attached to the baby dries up and falls off after a few days,
• The navel shows where the umbilical cord had been attached to the baby's body.
• By three months the fate of the human fetus' cells has already been determined, after three months delivery of the fetus grows very rapidly.
• The Uterus increases in size as the fetus grows.
• In the ninth month, the fetus turns so that its head is positioned towards the opening of the uterus in the vagina.
• Changing concentrations of hormones and conditions in the muscles of the walls of the uterus are believed to start childbirth, which begins when the uterus muscles repeatedly contract.
• The series of contractions are called labor.
• Labor is very hard work for the mother.

Lactation

• Lactation is stimulated by hormones from the pituitary.
• Milk flow occurs two days after the baby is born and is preceded by colostrum flow.
• Colostrum is watery, yellowish-white with the same composition as milk, but with more protein and less fat.
• When the baby suckles the nipple, nerve impulses travel to the hypothalamus of the mother, causing the posterior pituitary to release oxytocin, which causes the breasts to produce milk flow.

Semen

• The primary reproductive organ in the male is the pair of testes (testicles) contained in a sac called the scrotum.
• The Scrotum hangs from the body.
• Hundreds of millions of sperm cells are produced in the testicles.
• Sperm cells pass through the sperm duct and fluid is added, with the resulting mixture of fluid and sperm cells is called semen.
• Semen/fluid is produced by the seminal vesicles, the prostate gland, and the Cowper's glands.
• The fluid produced from the Seminal Vesicles and other glands makes the sperm cells active, and helps provide the proper chemical conditions for the sperm.
• Sperm can live for about three days in the vagina as a result of this fluid.
• Sperm cells move from the testes through the sperm duct to the urethra, and then out through the penis. The penis is used to inject sperm cells through urethra into the vagina. Then Sperm cells move to the uterus and proceed into the fallopian tube, uniting with an egg cell.
• Men release mature sperm anytime from puberty to old age.
• Human males do not have a breeding season.

Reproduction in Mammals

• Mammals nourish developing embryo inside the uterus.
• The placenta provides needed oxygen and nutrients to the developing embryo and also carries away waste.
• The embryo floats inside a fluid-filled sac.
• Young Mammals are born when the embryo had reached a level of development.
• Young Mammals starts to live outside the mother's body and continues to receive nourishment from the mother through the mammary glands.
• Mammary glands allow the newborns to suckle milk from mammales.
• Mammals differ in the number of offspring they can have at a time, and they may only produce one egg at a time.
• Eggs of mammals are smaller than eggs of birds and reptiles.
• Mammals normally give birth to one offspring at a time.
• Sex organs in vertebrtaes produce sex cells and also chemical substances called hormones.
• The Testes produce testosterone at large amounts.
• The ovaries in females produce estrogen in large amounts.
• Some Mammals such as rats and mice have shorter cycles, where as others have definite breeding seasons.
• Rats and mice sexually females come into heat and are ready to breed and reproduce every 5 days, where as dogs come into heat every 6 months, lasting 18-22 days.
• The Period between fertilization and the birth if the offspring differs widely among various animals.

Fertilization

• Many animal species fertilize the eggs and nourish the developing embryo inside their bodies.
• The embryo is said to undergo internalfertilization
• More offspring will survive and grow.
• Copulation fertilizes the egg in a female’s body.
• Timing is important in the internal fertilization since the lifespan of the sperm cell is short

External and Internal Fertilization

• Animals reproduce sexually in various ways.
• Aquatic animals release eggs and sperm directly into water to fertilize (External).
• Marine/Freshwater animals release million of eggs into water.
• Male animal release Sperm at the same time.
• The sperm eggs mix in the water by water movement.
• Likewse; Oysters, clams, starfish, jellyfish and marine worms discharge sex cells into the water.
• Those Mammals does not take core or the offspring.
• Among sharks/octopuses, fertilization s internal.
• Sharks uses modfied fin sturctures while octopuses modfied arms to transfer sperm directly to the other female animal.
• Frogs/Toads/Salamanders clasps he female frog in unique ways fertilizing their eggs.
• The amle from enable it by releasing the eggs with their borelegs that make their eggs fertilize.
• Fertilzation happens in the water due the sperm cells so those are External.
• Land animals, still had to unite sperm theegg fertilization.
• Animals such as insects/frogs, layeggs in most places.
• Some frogs/species make larval stages.
• Most land animals, inject and makes the sperm inside a Female inside body.
• A Female Animal requires a sperm to swim.
• Earthworms make make sex organs in the same individuals but it’s not self-fertilization.
• And makes exchanged individuals and matng.

Sexual Reproduction

• Sexual reproduction happens in many sex cells produce.
• Sex cells produced.
• Those cells produced during meioisis.
• A Female, makes eggs while testicle make sperms sellas it’s form to make a zygote.
• Zygote s Diplod
• Fertiziler animal cannot let protective covering. The egg birds/repetitlie have minerals develop embryo and water/nutriends.

Asexual Reproduction

• Parthenogenesis is a form of Asexual. And makes Female reproduce with molting.
• Regeneration an fragmented Is asexual reprodcution and is single parent type.
• Makes small and have individual starfish types.
• Buddings includes involves slitting individual for small animals.
• Have projections and buddy.

Fragmentation and Planaria

• Fragmentation and regeneration is a type of asexual reproduction wherein a single parent breaks out into parts, giving rise to new individuals.
• Planaria and starfish are examples of animals exhibiting asexual reproduction.

Asexual reproduction

• Asexual reproduction is the type of reproduction that creates genetically identical offspring, and are considered clones of the parents.
• Asexual reproduction in plants may occur from vegetative parts (stem, roots, and leaves), called vegetative reproduction.
• Some plants can give rise to new life using modified or specialized stems, such as stolons, tubers, bulbs, and rhizomes.

How do Plants reproduce?

• Plant reproduction is the process of generating new plant individuals, there are two types:
  • Sexual Reproduction
  • Asexual Reproduction

What Parts of a Flower do?

• A flower has highly specialized males and females that can make Reproductive organs.
• The Pistil is made of Stigma that has Female Reproductive with Ovary/Style and has ovule that contain the egg nuclei.
• Stamens, on the other hand, are made of pollen grains. It has the sperm of the male reproductive system (Anther).

Parts of a Seed

• The Seed consist of endosperm/embryo/seed coat.
• The seed consist to make a seed coat where internal/external facor is placed.
• Made of the hupocotyl, epicotyl and radicles.
• Is external wth wind/water and makes help help dispersal seeds.
• Seed germination causes early plant development and maturity where lead to the reproduction.
• The hypocotyl, made to stem while Radicle is made to the embryic root .
• The epicotyl makes hte stems and makes the shoots for seedisig.

Diagram

• In Diagrams on seed shows that cotyledons while the top shows the radicle, where it had external leaves.

Seed Dispersal

• After the seeds form and mature, they are scattered into a environment for seed dispersal.
  • Seed Dispereal Makes survival importnant o the plants species.
  • The Seed Coat protects Seeds.
• Embryo develops new parts for the plant; Plumule/Epicotyl/Hypocothyl.
• Store food to corn: seed coat where protects/ and new plant.

Types of Asexual Reproduction

• Type: Fission
  • Description: Occurs when a parent cell splits into two identical, daughter cells of the same size
  • Example Organisms: Bacteria, Protists, Unicellular Fungi
• Type: Fragmentation
  • Description: Occurs when a parent organism breaks into fragments or pieces and each fragment develops into a new organism
  • Example Organisms: Starfish, some worms, fungi, plants, lichens
• Type: Budding
  • Description: Occurs when a parent cell forms a bubble-like bud. The bud stays attached to the parent cell while it grows and develops. When the bud is fully developed, it breaks away from the parent cell and forms a new organism
  • Example Organisms: Yeast
• Type: Fragmentation
  • Description: occurs when new individuals are formed without the production of seeds or spores.
  • Example Organisms: Plants
• Type: Many plant and some: Any form of reproduction that does not involve a male gamete
  • Description: agamogenesis