Human Body Systems & Celestial Events

• The notes cover the circulatory, respiratory, and reproductive systems, as well as solar and lunar eclipses, and moon orbits.

Circulatory System

• The major parts are the heart, blood, and blood vessels.
• Blood enters the right atrium from the body and passes through the tricuspid valve into the right ventricle.
• The right ventricle pumps deoxygenated blood to the lungs via the pulmonary artery, where blood picks up oxygen and releases carbon dioxide.
• Oxygenated blood returns to the left atrium via the pulmonary veins, then passes through the bicuspid (mitral) valve into the left ventricle.
• The left ventricle pumps oxygenated blood through the aorta to the rest of the body.

Respiratory System

• Responsible for gas exchange—bringing in oxygen and expelling carbon dioxide.
• Air enters through the nose or mouth and passes through the pharynx, epiglottis, and larynx, then moves down the trachea (windpipe).
• The trachea branches into two bronchi, leading to each lung, which split into smaller tubes called bronchioles.
• At the end of bronchioles are tiny air sacs called alveoli.
• Oxygen diffuses into the blood, carbon dioxide moves from the blood into the alveoli to be exhaled.
• Gas exchange: oxygen moves from the alveoli into the blood and carbon dioxide moves from the blood into the alveoli.

Solar and Lunar Eclipses

• A solar eclipse occurs when the Moon comes between the Sun and Earth, blocking sunlight.
• A lunar eclipse happens when Earth comes between the Sun and Moon, casting a shadow on the Moon.

Types of Solar Eclipses

• Total Solar Eclipse: when the Moon completely covers the Sun, the Sun’s corona is visible as a glowing halo.
• Total Solar Eclipse: Occurs only along a narrow path on Earth (path of totality) and can last up to 7 minutes and 32 seconds.
• Partial Solar Eclipse: the Moon covers only part of the Sun, appearing as a crescent, visible over a broader area than a total eclipse.
• Annular Solar Eclipse: occurs when the Moon is at its farthest point from Earth (apogee) and appears smaller, not fully covering the Sun.
• Annular Solar Eclipse: Creates a "ring of fire" effect around the Moon and is only visible within a specific path.

Types of Lunar Eclipses

• Total Lunar Eclipse: The Moon moves entirely into Earth’s umbra (full shadow), appearing red due to atmospheric scattering ("Blood Moon").
• Total Lunar Eclipses can last up to 1 hour and 47 minutes, and it's visible from anywhere on Earth where the Moon is above the horizon.
• Partial Lunar Eclipse: A portion of the Moon passes through Earth's umbra, appearing partially darkened.
• Penumbral Lunar Eclipse: The Moon moves through Earth’s penumbra (outer shadow), causing a slight dimming, often hard to notice.

Moon Orbits and Locations

• Perigee: The Moon’s closest point to Earth (~363,300 km away) making the Moon appear slightly larger.
• Apogee: The Moon’s farthest point from Earth (~405,500 km away) making the Moon appear smaller.
• Ecliptic Plane: The imaginary plane in which the Earth's orbit around the Sun and the Moon's orbit around Earth lie.

Reproductive System

• Responsible for producing gametes (sperm and egg cells), enabling fertilization, and supporting pregnancy in females.

Male Reproductive System

• Testes: Produce sperm and testosterone.
• Epididymis: Stores and matures sperm.
• Vas Deferens: Transports sperm to the urethra.
• Seminal Vesicles: Add fluid to nourish sperm.
• Prostate Gland: Secretes a fluid to protect sperm.
• Cowper’s Gland: Produces a lubricating fluid.
• Urethra: Transports sperm out of the body during ejaculation.
• Penis: Delivers sperm to the female reproductive tract.

Female Reproductive System

• Ovaries: Produce eggs and secrete estrogen and progesterone.
• Fallopian Tubes: Transport the egg from the ovaries to the uterus where fertilization occurs.
• Uterus: Supports embryo implantation and fetal development.
• Cervix: The lower part of the uterus, which opens into the vagina.
• Vagina: Birth canal and passage for sperm entry.

Fertilization and Pregnancy

• Sperm travels through the vagina, cervix, and uterus to the fallopian tube.
• A single sperm fuses with an egg, forming a zygote which undergoes cell division, forming a blastocyst.
• The blastocyst implants into the uterus, marking the start of pregnancy.

Pregnancy Trimesters

• First Trimester (Weeks 1-12): Formation of limbs, brain, and major organs, by 8 weeks, it is called a fetus.
• First Trimester: The placenta develops to provide nutrients and oxygen.
• Second Trimester (Weeks 13-26): Fetus develops facial features, movements begin, and the nervous system matures, and hearing develops.
• Second Trimester: Hair and nails start forming.
• Third Trimester (Weeks 27-Birth): Rapid weight gain and lung development.
• Third Trimester: The fetus moves into a head-down position for birth and by birth, the baby weighs between 6-9 pounds.

Childbirth and Labor Stages

• Dilation Stage: Contractions begin, and the cervix dilates to 10 cm, the amniotic sac may rupture ("water breaking").
• Expulsion Stage: The baby is pushed out through the birth canal.
• Placental Stage: The placenta is expelled after the baby is born.

Hormones In Reproduction

• Testosterone: Stimulates sperm production and male secondary sexual characteristics.
• Estrogen: Regulates the menstrual cycle and develops female secondary sexual characteristics.
• Progesterone: Maintains pregnancy by thickening the uterus lining.
• FSH (Follicle-Stimulating Hormone): Stimulates egg and sperm production.
• LH (Luteinizing Hormone): Triggers ovulation and testosterone production.
• Oxytocin: Induces labor contractions and milk ejection.

Overview of circulatory and respiratory systems: heart, blood vessels, gas exchange. Also covers reproductive systems, solar & lunar eclipses, and moon orbits.