Reproductive and Urinary Systems Flashcards

Sexual Reproduction

• Most organisms shuffle and exchange genetic information, possessing two sets of genetic information from each parent.
• Sexual reproduction is the union of two sex cells, forming a new individual.
• Female sex cells are eggs, while male sex cells are sperm. Gametes is the general term for both.
• Gametes are created through meiosis.
• Adult cells contain two sets of homologous chromosomes, one from each parent.
• An organism with two sets of chromosomes is diploid.
• Meiosis reduces the chromosome number, making the cell haploid.
• Gametes unite during fertilization, forming a diploid zygote.

Fertilization

• External fertilization occurs when eggs are fertilized by sperm in an external environment, common in aquatic animals.
  • Gametes have short lifespans, and many are lost to predators or other environmental factors.
• Internal fertilization involves sperm deposition in or near the female reproductive tract.
  • An example is the mudpuppy, where the male deposits a spermatophore (sperm and nutrients) near the female.
  • The female picks up the spermatophore with her cloaca, leading to internal fertilization.
• Most terrestrial animals, including humans, practice internal fertilization.

Female Reproductive System

• The female gonads (ovaries) produce eggs through oogenesis.
• Ovaries are held in place by connective tissue ligaments in the pelvic cavity.
• Internally, the ovary contains connective tissue with eggs (ova) in various stages of maturation.
• Ovulation: The egg grows, moves near the ovary surface, and is swept into the oviduct (fallopian tube).
• Fertilization happens within the oviduct.
• After fertilization, the egg travels to the uterus and embeds in the endometrial tissue.
• If unfertilized, the egg passes through the vagina during menstruation.
• A female releases approximately 300-500 eggs in her lifetime, about once a month, from puberty to menopause.
• Example: A woman menstruating from age 14 to 45 releases approximately 372 eggs, assuming one egg per cycle.
• The vagina opens to the vulva, the external female organs.
• The female urinary and reproductive tracts are separate.

Endometriosis

• Endometriosis is a common gynecological disease where endometrial tissue grows outside the uterus, typically on pelvic organs.
• These growths are referred to as lesions, implants, or nodules.
• Possible causes include retrograde menstrual flow, inherited traits, genetic errors, or environmental factors.
• Estrogen promotes the growth of endometriosis.
• Symptoms include painful periods, painful intercourse, fatigue, abdominal/lower back pain, and irregular bleeding.
• Estimated 5.5 million women in North America have endometriosis.
• May lead to lower fertility rates or infertility.
• Diagnosis:
  • Ultrasound: Uses sound waves to create an image.
  • Magnetic Resonance Imaging (MRI): Uses magnets and radio waves to create an image.
  • Laparoscopy: A surgeon inflates the abdomen with gas and uses a laparoscope to view reproductive organs for signs of endometriosis. A biopsy can confirm the diagnosis.

Male Reproductive System

• The male urinary and reproductive systems are combined.
• Testes are located outside of the body, within the scrotum, a skin-covered sac suspended from the groin.
• Spermatogenesis (sperm production) must occur at a temperature slightly lower than normal body temperature.
• The scrotum cools the sperm to below body temperature.
• Sperm cells are produced in seminiferous tubules within the testes.
• Collecting ducts in the testes store sperm.
• The seminiferous tubules join to become the epididymis, where sperm cells are stored and matured.
• Tubes leading from the epididymis are the vas deferens.
• The vas deferens empty into the urethra, located inside the penis.
• The urethra carries both urine and semen out through the penis.
• Semen: Mixture of sperm and accessory gland secretions.
  • A single ejaculate of about 3.5 mL contains approximately 400 million sperm cells.
• Accessory glands: Seminal vesicles, prostate glands, and bulbourethral glands.
  • Secretions nourish sperm, provide appropriate pH, and lubricate the tract.
• Prostate gland secretions neutralize the acidic vaginal environment, crucial for sperm motility.
• Bulbourethral glands produce mucous.
• Seminal vesicles provide nourishment-rich secretions.

Prostate Cancer

• Strikes 1 in 6 men in America.
• Symptoms include frequent urination, painful urination, difficulty starting or holding back urination, difficulty in having an erection, painful ejaculation, blood in semen and urine, pain in the lower back, hips, or thighs.
• Risk factors:
  • Age: Mostly men over 55, average age of diagnosis is 70.
  • Family history: Higher risk if a father or brother is diagnosed before 60.
  • Race: More common in men of African American and White descent, least common in Asian and American Indian men.
  • Dietary factors: High-fat diet increases risk, high fruit and vegetable diet decreases risk.
• High survival rate: About 89% of men diagnosed survive for five years, 63% survive 10 years or more, due to increased treatment options.

Male Infertility

• Sperm count has dropped over the past 30 years.
  • In the 1970s, sperm counts averaged 100 million sperm per mL of semen.
  • Today the average is about 60 million.
  • Fertility is impaired below 35 million, and sterility is considered below 20 million.
• Causes: Environmental factors, drug usage, alcohol abuse, and cigarette smoking.

Fertilization, Pregnancy, and Birth

• Fertilization with the establishment of a pregnancy is considered to be conception.
• Fertilization is the fusion of eggs and sperm, occurs in the oviduct.
• The zygote travels toward the uterus, undergoing mitosis.
• The zygote must embed within the uterine wall for pregnancy to be established.
• The zygote becomes a solid mass of cells, a morula.
• The morula continues dividing and becomes a blastocyst.
• The blastocyst implants within the uterine wall within the first two weeks of fertilization.
• This stage of development is called blastogenesis, literally the creation of the blastocyst.
• The next stage of development is called gastrulation, which is the stage where the gut is formed. The embryo develops a tube that becomes the gut through a series of folding.
• The embryo is encased in a fluid-filled sac called the amnion.
• Another membrane, the chorion, surrounds the embryo. It will eventually fuse with maternal tissue and become the placenta.
• The placenta:
  • A fetomaternal organ, made of fetal (villous chorion) and maternal components.
  • Meets the nutritional needs of the embryo.
  • Site of gas exchange and waste removal.
  • Produces hormones that prevent uterine wall shedding.
• Any molecule the mother consumes, the embryo also consumes (including drugs and alcohol).
• The fetus is connected to the placenta via the umbilical cord.
• The umbilical cord contains one umbilical vein and two umbilical arteries.
  • The umbilical vein carries highly oxygenated blood from the placenta towards the heart and other developing organ systems.
  • The umbilical arteries carry poorly oxygenated blood away from the heart of the embryo and toward the placenta.
• A placental membrane separates fetal and maternal blood.
  • Nutrients and other substances diffuse across the membrane, but blood is not shared.
• Major body parts are in place by the tenth week of pregnancy. After this, the embryo is considered a fetus.
• Human gestation is divided into three trimesters of about three months each.
  • The first trimester involves organogenesis, where many organ systems develop and go through a critical period.
  • The second trimester involves fetal growth. The mother may feel movements, and the pregnancy becomes visible. The fetal heartbeat can be heard with a stethoscope.
  • The third trimester involves continued fetal growth. Final differentiation of organs occurs, and the cerebrum grows rapidly.
• An infant born before 37 weeks is considered premature, but survival is likely if older than 30 weeks.

Asexual reproduction

• Asexual reproduction occurs when a parent produces genetically identical offspring via mitosis.
• Budding: A small part of the parent organism develops into a new individual. Buds can remain attached, forming a colony.
• Fragmentation: The body of the parent breaks into pieces, and each piece regenerates into a new organism. Starfish can reproduce this way.

Urinary System

• Principle function is removal of nitrogenous wastes and osmoregulation (maintaining salt concentrations).
• The main organ is the kidney.
• Includes the urinary bladder and associated ducts.
• The outer portion of the mammalian kidney is called the renal cortex, the inner portion is called the renal medulla.
• Within the medulla, there are about eight to ten cone-shaped renal pyramids.
• Each pyramid has a renal papilla with pores (openings of collecting ducts).
• Urine flows from collecting ducts to a renal papilla, then into the renal pelvis.
• Urine flows into the ureters and then to the urinary bladder.
• The urinary bladder can hold up to 800 mL of urine due to the special property of the epithelium.
• Urine passes through the urethra to the outside environment.
• Each kidney has more than a million functional units, called nephrons.
• A nephron consists of:
  • Bowman’s capsule: A cuplike structure connected to a long, coiled renal tubule.
  • Glomerulus: A cluster of capillaries within the Bowman’s capsule.
• Three main regions of the renal tubule:
  • Proximal convoluted tubule: Moves filtrate from the Bowman’s capsule.
  • Loop of Henle: A hairpin-shaped portion of the tubule.
  • Distal convoluted tubule: Conducts the filtrate to a collecting duct.
• Urine is produced in three steps: filtration, reabsorption, and secretion.
  • Filtration: Occurs around the glomerulus. The excretory tubule collects a filtrate from the blood. Water and solutes are forced by blood pressure across the selectively permeable membranes of a cluster of capillaries and into the excretory tubule.
  • Reabsorption: Allows regulation of blood chemistry by removing wastes, excess salts, and other materials while retaining molecules such as glucose and amino acids. The body reclaims valuable substances from the filtrate.
  • Secretion: Substances, such as toxins and excess ions, are extracted from body fluids and added to the contents of the excretory tubule.
  • Excretion: The filtrate leaves the system and the body.