BIO 182 Exam 3 PDF

Chapter 24 Learning Outcomes (Study Guide): What are the structures of the urinary system and how are they connected? ​ Structures: Kidneys, ureters, urinary bladder, urethra. ​ Connection: Kidneys filter blood to produce urine, which passes through the ureters to the bladder for stora...

Chapter 24 Learning Outcomes (Study Guide): What are the structures of the urinary system and how are they connected? ​ Structures: Kidneys, ureters, urinary bladder, urethra. ​ Connection: Kidneys filter blood to produce urine, which passes through the ureters to the bladder for storage. Urine is expelled through the urethra. What types of tissue surround the kidneys? What are the functions of each of these layers? Tissues: Renal capsule (protective layer), adipose capsule (cushioning), renal fascia (anchors the kidneys). Functions: ​ Renal capsule: Protects against infection and physical damage. ​ Adipose capsule: Provides cushioning and insulation. ​ Renal fascia: Anchors the kidneys to surrounding structures. What are the three major regions of the kidneys? Where are the renal pyramids located? Regions: Cortex, medulla, pelvis. Renal pyramids: Located in the medulla, these cone-shaped structures are involved in urine processing. After urine is released from the renal papillae, by what path does it make its way to the urinary bladder? Urine flows from renal papillae → minor calyx → major calyx → renal pelvis → ureter → urinary bladder. How does blood flow to and from the kidneys? Which class of artery in this blood flow pathway has no vein counterpart? Blood Flow: Renal artery → afferent arterioles → glomerulus → efferent arterioles → peritubular capillaries → renal vein. No Vein Counterpart: The afferent arterioles have no direct venous counterpart. What is a nephron? What is the pathway of filtrate flow through a nephron? Nephron: Functional unit of the kidney, involved in filtering blood and forming urine. Filtrate Pathway: Glomerulus → Bowman's capsule → proximal convoluted tubule → nephron loop (loop of Henle) → distal convoluted tubule → collecting duct. What is the structure of a renal corpuscle? What critical physiological event occurs here? Structure: Composed of Bowman's capsule and glomerulus. Function: Filtration of blood to form filtrate; the first step in urine production. What type of capillary is a glomerulus? ​ The glomerulus consists of fenestrated capillaries, allowing for high filtration. How does the structure of the renal tubule change throughout the nephron? What would you expect to be true of regions of the renal tubule with more microvilli? Structure Changes: The tubule becomes narrower and more convoluted from the proximal to the distal end. Microvilli: Regions with more microvilli (proximal tubule) are involved in more reabsorption, increasing surface area for absorption. What is a renal collecting duct? Where does this structure take filtrate? Structure: The collecting duct collects filtrate from multiple nephrons. Pathway: Takes filtrate from the distal convoluted tubule to the renal pelvis. What is a kidney stone? How do these develop? Definition: Hard deposits of minerals and salts that form in the kidneys. Development: Occur when urine becomes concentrated, causing crystals to form. What are the similarities and differences between cortical and juxtamedullary nephrons? Which type does a typical kidney have more of? Which type plays the biggest role in regulating the concentration of urine? ​ Cortical Nephrons: Located primarily in the cortex; involved in general filtration. ​ Juxtamedullary Nephrons: Have long loops of Henle, play a major role in urine concentration. ​ More Common: Cortical nephrons are more numerous. ​ Urine Concentration: Juxtamedullary nephrons play the biggest role. What is the difference between tubular reabsorption and tubular secretion? Where in the nephron does most reabsorption take place? ​ Reabsorption: Movement of substances from filtrate back into the blood. ​ Secretion: Movement of substances from the blood into the filtrate. ​ Primary Reabsorption Site: Proximal convoluted tubule. How does the structure of the glomerulus regulate renal filtration? What substances are typically filtered from the blood into the filtrate, and which are not? Filtration: The glomerulus filters blood into Bowman's capsule. Filtered Substances: Water, ions, glucose, urea; Not Filtered: Large proteins, blood cells. What are glomerular hydrostatic pressure, capsular hydrostatic pressure, and glomerular colloid osmotic pressure? How would you use these values to determine net glomerular filtration pressure? Glomerular Hydrostatic Pressure: Pressure exerted by blood in glomerular capillaries (drives filtration). Capsular Hydrostatic Pressure: Resistance from fluid already in Bowman's capsule. Glomerular Colloid Osmotic Pressure: Osmotic pressure exerted by proteins in the blood. Net Filtration Pressure: Calculated by subtracting opposing pressures from the glomerular hydrostatic pressure. Why is it important to a functioning kidney that net glomerular filtration pressure is a positive value? Positive pressure ensures that filtration occurs, moving substances from the blood into the nephron for processing. How does constriction and dilation of the afferent and efferent arterioles affect glomerular filtration pressure? What is the relationship between glomerular filtration pressure and glomerular filtration rate? Constriction of Afferent Arteriole: Decreases filtration pressure. Constriction of Efferent Arteriole: Increases filtration pressure. Glomerular Filtration Rate (GFR): Directly related to filtration pressure; higher pressure increases GFR. How does the renin-angiotensin pathway affect glomerular filtration rate? ​ Renin release from the kidneys increases blood pressure and reduces sodium loss, which can alter GFR and fluid balance. What are the different pathways that reabsorb solutes can take to move from the renal tubule back into the blood? What about secreted substances? ​ Reabsorption: Substances move through the renal tubule cells into the peritubular capillaries. ​ Secretion: Substances move from the blood into the renal tubule for excretion. What kind of molecules are reabsorbed from the renal tubule? What percentage of the amount of these solute types get reabsorbed? ​ Reabsorbed: Water, glucose, amino acids, ions. ​ Percentage: ~99% of filtered water and most solutes are reabsorbed. How does reabsorption of glucose and bicarbonate molecules occur in the kidney? Glucose: Actively transported in the proximal convoluted tubule. Bicarbonate: Reabsorbed through a combination of active transport and chemical reactions in the proximal tubule. How does water reabsorption in the renal tubule work? What type of channel greatly facilitates this process? ​ Water reabsorption is primarily facilitated by aquaporin channels in the renal tubule, particularly in the proximal tubule and collecting ducts. If material is not reabsorbed from the kidney tubule, where does it end up? ​ Material not reabsorbed from the tubule ends up in the urine for excretion. What is the difference between obligatory and facultative water reabsorption? Where do these processes occur? Obligatory: Happens in the proximal tubule and descending loop, follows osmotic gradients. Facultative: Regulated by hormones (e.g., ADH), occurs in the distal tubule and collecting ducts. What is the descending limb of the nephron loop (loop of Henle) permeable to? What about the ascending limb? Descending Limb: Permeable to water, but not solutes. Ascending Limb: Permeable to solutes (Na+, Cl−), but not water. How does the "countercurrent multiplier" mechanism of the nephron loop of juxtamedullary nephrons set up a solute of gradient outside of the nephron loop in the medulla? Where is solute concentration the highest? Where is it the lowest? ​ The nephron loop creates a concentration gradient in the renal medulla by pumping solutes out of the ascending limb while water leaves the descending limb. ​ Solute Concentration: Highest in the medulla, lowest in the cortex. What two things are required for water to be reabsorbed from the distal tubule and collecting ducts? How is this process hormonally controlled? Requirements: Medullary osmotic gradient and the presence of ADH (antidiuretic hormone). Hormonal Control: ADH increases water reabsorption by making the collecting ducts more permeable to water. How does the medullary osmotic gradient allow for the formation of concentrated urine? Why is it the case that dilute urine can be formed even with the presence of the medullary osmotic gradient? Gradient: The high osmolarity in the medulla allows for the reabsorption of water, concentrating urine. Dilute Urine: Can form if ADH is low or if the kidney does not use the medullary gradient. What type of epithelium lines the ureters and urinary bladders? What type of muscle is found in the urinary bladder? Epithelium: Transitional epithelium, which can stretch. Muscle: Smooth muscle in the bladder (detrusor muscle). How does urine travel out of the urinary bladder? How is this route different in a male vs female urinary system? Urination Pathway: Bladder → urethra. Male vs. Female: In males, the urethra is longer and passes through the penis; in females, it is shorter and leads directly to the external opening. How is the urination (micturition) reflex controlled by the nervous system? ​ The micturition reflex is controlled by the autonomic nervous system (involuntary) and voluntary control over the external sphincter. (a signal that tells you when your bladder is full.) Which two sphincters control the release of urine into the environment? Which is under voluntary and which under involuntary control? ​ Internal Sphincter: Involuntary control, smooth muscle. ​ External Sphincter: Voluntary control, skeletal muscle. Chapter 25 Learning Outcomes (Study Guide): What is an electrolyte? What are some good examples of electrolytes in the human body? ​ Electrolytes: Charged particles (ions) that conduct electricity in water. ​ Examples: Sodium (Na⁺), potassium (K⁺), chloride (Cl⁻), calcium (Ca²⁺), bicarbonate (HCO₃⁻), phosphate (PO₄³⁻). In what different "compartments" do you find water in the body? In which is the most water found? Compartments: ​ Intracellular fluid (ICF): Inside cells (~2/3 of total body water). ​ Extracellular fluid (ECF): Outside cells (~1/3 of body water), including interstitial fluid and plasma. Most Water: Found in intracellular fluid. What ion is in the highest concentration in extracellular fluid? What about intracellular fluid (cytosol)? Extracellular Fluid: Sodium (Na⁺) is the most abundant ion. Intracellular Fluid: Potassium (K⁺) is the most abundant ion. Extracellular fluid and blood plasma are essentially chemically identical except for which component? Main Difference: Blood plasma contains proteins (e.g., albumin) that are largely absent in other extracellular fluids like interstitial fluid. What happens to a cell in a hypertonic, isotonic, and hypotonic environment? Hypertonic: Cell shrinks as water moves out. Isotonic: No net movement of water, cell maintains its shape. Hypotonic: Cell swells as water moves in. What is the state of a human cell during dehydration? What happens to these cells after water is ingested? Dehydration: Cells lose water and shrink (crenation), impairing function. After Water Intake: Cells rehydrate and return to normal size and function. How does a human acquire water throughout the day? How do they lose it? How much water does a human need to ingest during one day? Acquisition: ​ Drinking liquids, consuming food, and metabolic water (produced during cellular respiration). Loss: ​ Urine, sweat, respiration, and feces. Water Requirement: A typical adult needs about 2.5 liters/day. What is the "principle of mass balance" and how does this apply to fluid balance in the body? ​ Principle of Mass Balance: The amount of fluid entering and leaving the body must be balanced. ​ Fluid Balance: The body maintains this balance by regulating intake, excretion, and storage of water. What portion of the brain initiates the thirst response? Does a person need to be dehydrated to feel thirsty? Brain Region: The hypothalamus initiates the thirst response. Thirst Without Dehydration: Thirst can also occur due to factors like salt intake, dry mouth, or even psychological triggers. What is hypernatremia? What is hyponatremia? What major effects do these states have on the body? Hypernatremia: High sodium levels in the blood, leading to dehydration, confusion, and possibly seizures. Hyponatremia: Low sodium levels, causing swelling of cells, headache, nausea, and potentially coma. What is hyperkalemia? What is hypokalemia? What major effects do these states have on the body?  ​ Hyperkalemia: High potassium levels, leading to muscle weakness, cardiac arrhythmias, and potential heart failure. ​ Hypokalemia: Low potassium levels, causing muscle cramps, weakness, and arrhythmias. What is hypercalcemia? What is hypocalcemia? Hypercalcemia: High calcium levels, leading to bone pain, kidney stones, and cardiac issues. Hypocalcemia: Low calcium levels, leading to muscle spasms, tetany, and cardiac arrhythmias. What is an acid? What is a base? What is a buffer? Acid: A substance that donates protons (H⁺) in solution. Base: A substance that accepts protons (H⁺). Buffer: A solution that resists changes in pH by neutralizing excess acids or bases. What is the biggest source of acid in the human body? ​ The primary source is carbonic acid (H₂CO₃), which forms from CO₂ during cellular respiration. How does generation of bicarbonate anion help to regulate body pH levels? How does the secretion of hydrogen ions also accomplish this? ​ Bicarbonate Anion (HCO₃⁻): Acts as a buffer by neutralizing excess hydrogen ions, preventing blood from becoming too acidic. ​ Hydrogen Ion Secretion: Kidneys secrete H⁺ into the urine to lower blood acidity when needed. How does a change in respiratory rate affect blood pH levels? Increased Respiratory Rate: Expels more CO₂, reducing acidity and raising pH (making blood more alkaline). Decreased Respiratory Rate: CO₂ builds up, increasing blood acidity (lowering pH, makes blood more acidic) What is alkalosis? What is acidosis? How do changes in metabolism and respiration compensate during these states? ​ Alkalosis: A condition where the blood pH is above 7.45, often due to excessive base or loss of acids. ​ Acidosis: A condition where the blood pH is below 7.35, often due to excessive acid or loss of bases. ​ Compensation: ○​ In alkalosis, the body decreases respiratory rate and the kidneys retain H⁺ to lower pH. ○​ In acidosis, the body increases respiratory rate and kidneys excrete H⁺ and retain bicarbonate to raise pH. Chapter 26 Learning Outcomes (Study Guide): What is a chromosome? What are homologous chromosomes? Chromosome: A thread-like structure made of DNA and proteins that carries genetic information. Homologous Chromosomes: A pair of chromosomes, one from each parent, that are similar in shape, size, and genetic content but may carry different versions (alleles) of a gene. What is the difference between a diploid and a haploid cell? Diploid (2n): Cells with two sets of chromosomes (one from each parent), typical of somatic cells. Haploid (n): Cells with one set of chromosomes, typical of gametes (sperm and egg cells). What are the stages of meiosis? What is the end product of the meiosis of a single cell? Stages of Meiosis: ​ Meiosis I: Prophase I, Metaphase I, Anaphase I, Telophase I ​ Meiosis II: Prophase II, Metaphase II, Anaphase II, Telophase II End Product: Four genetically unique haploid cells (gametes). At what point during meiosis do cells go from being diploid to being haploid? Cells go from diploid to haploid during Meiosis I, specifically after the separation of homologous chromosomes. What is a gamete? Are gametes haploid or diploid? ​ Gamete: A reproductive cell (sperm or egg) that fuses during fertilization to form a zygote. ​ Haploid: Gametes are haploid, containing one set of chromosomes. What two mechanisms provide for the genetic uniqueness of gametes? When during meiosis do these mechanisms occur? Mechanisms for Uniqueness: 1.​ Independent Assortment: Homologous chromosomes are randomly distributed into gametes during meiosis. 2.​ Crossing Over: Homologous chromosomes exchange genetic material during meiosis I, creating genetic variation. These mechanisms occur during Meiosis I. What are some differences between meiosis and mitosis? ​ Meiosis: Results in four non-identical haploid cells, involves two rounds of division (Meiosis I and II), and creates gametes. ​ Mitosis: Results in two identical diploid cells, one round of division, and creates somatic cells. What are the organs of the male reproductive system, and where are they located? ​ Organs:  ○​ Testes: Produce sperm and testosterone, located in the scrotum. ○​ Epididymis: Stores sperm, located on top of the testes. ○​ Vas deferens: Transports sperm, located from the epididymis to the urethra. ○​ Seminal Vesicles: Produce seminal fluid, located behind the bladder. ○​ Prostate Gland: Secretes fluids that nourish sperm, located below the bladder. ○​ Penis: External organ for urination and reproduction. What type of tissue makes up the penis? How do these tissue types contribute to its reproductive function? Tissues: Made up of erectile tissue (corpora cavernosa and corpus spongiosum), which engorges with blood during arousal to facilitate erection and penetration during intercourse. What are the male gonads? How are they structured? ​ Gonads: The testes. ​ Structure: Contain seminiferous tubules where sperm is produced, and interstitial cells that produce testosterone. Where is the site of sperm cell formation? What path do sperm travel from their site of formation to the external environment? ​ Site: Sperm are formed in the seminiferous tubules of the testes. ​ Travel Path: Seminiferous tubules → Epididymis → Vas deferens → Ejaculatory duct → Urethra → External environment. What are the glands that contribute to seminal fluid? Where are they located? Glands: 1.​ Seminal Vesicles: Produce the majority of seminal fluid. 2.​ Prostate Gland: Secretes prostate fluid. 3.​ Bulbourethral Glands: Secrete a lubricating fluid. Location: Around the base of the bladder and the urethra. What is semen? How is this different from sperm? Semen: A fluid containing sperm and secretions from the prostate, seminal vesicles, and bulbourethral glands. Difference from Sperm: Semen is the fluid that transports sperm; sperm is the actual male gamete. What is spermatogenesis? What type of cell does this process begin with, and where does this process occur? Spermatogenesis: The process by which sperm are produced from spermatogonia (diploid germ cells) in the seminiferous tubules of the testes. Begins With: Spermatogonia. Occurs in: Seminiferous tubules. What is the importance of the blood-testis barrier during spermatogenesis, and which cells provide this barrier? Barrier: Protects developing sperm from immune system attack and ensures proper spermatogenesis. Provided by: Sertoli cells. What is spermiogenesis? What happens to the sperm cell during this process? ​ Spermiogenesis: The final stage of spermatogenesis where spermatids mature into sperm. ​ Changes: Spermatids develop a flagellum (tail), condense their nucleus, and gain a head with an acrosome for fertilization. What roles do the hormones LH, FSH, and testosterone play in male reproductive system regulation? LH (Luteinizing Hormone): Stimulates testosterone production from Leydig cells. FSH (Follicle-Stimulating Hormone): Stimulates Sertoli cells to support sperm development. Testosterone: Promotes spermatogenesis, development of male secondary sex characteristics, and libido. What are the internal organs of the female reproductive system, and how are they structured? Organs: ​ Ovaries: Produce eggs (oocytes) and hormones (estrogen, progesterone). ​ Fallopian Tubes: Transport eggs from the ovaries to the uterus. ​ Uterus: Where embryo implants and develops.  ​ Cervix: Lower part of the uterus, connects to the vagina. ​ Vagina: Birth canal and passage for menstrual flow. What structures make up the external genitalia of the female reproductive system? Where are these located, and what is the function of each? Structures: ​ Vulva (external part of the female genitalia). ​ Labia Majora/Minora: Outer and inner folds of skin that protect the vaginal and urethral openings. ​ Clitoris: Sensitive organ involved in sexual arousal. Function: Protection, sexual arousal, and passage for childbirth. Though the breasts are technically part of the integumentary system, why are they often studied with the reproductive system? What type of tissue do you find in breasts? Breasts: Though part of the integumentary system, they are studied with the reproductive system because they produce milk for infant nourishment. Tissue: Composed of glandular tissue (mammary glands) and adipose tissue. What occurs during the process of oogenesis? How is this similar to and different from spermatogenesis? Oogenesis: The production of eggs from oogonia (female germ cells). Differences: Oogenesis results in one functional egg per cycle, while spermatogenesis produces four sperm. Oogenesis begins before birth, pauses, and resumes at puberty. What are the different phases of the ovarian cycle? What type of cell is released during the ovulation phase? Phases: 1.​ Follicular Phase: Development of follicles in the ovary. 2.​ Ovulation: Release of a mature egg from the ovary. 3.​ Luteal Phase: Formation of the corpus luteum, which secretes progesterone. Cell Released During Ovulation: A secondary oocyte. How does an ovulated cell move into the uterine (fallopian) tubes? The secondary oocyte is swept into the fallopian tube by fimbriae (finger-like projections) and ciliary action. How do LH, FSH, and estrogens regulate the ovarian cycle? FSH: Stimulates follicular development in the ovaries. LH: Triggers ovulation and the formation of the corpus luteum. Estrogen: Prepares the endometrium for potential implantation. Where in the uterus would an embryo implant? How does this tissue change during the uterine cycle? ​ Implantation: Occurs in the endometrium (inner lining of the uterus). ​ Uterine Cycle Changes: The endometrium thickens during the proliferative phase and sheds during menstruation if no pregnancy occurs. What is menses (menstruation/"period")? When during the uterine cycle does this occur? Menses: The shedding of the uterine lining when pregnancy does not occur, leading to bleeding. Occurs: During the menstrual phase of the uterine cycle. Can you match the phases of the uterine and ovarian cycles, as well as the hormonal signals that stimulate these phases? Follicular Phase (Ovarian Cycle) → Proliferative Phase (Uterine Cycle) → Estrogen rises. Ovulation → LH surge triggers ovulation. Luteal Phase → Secretory Phase → Progesterone rises. What is the LH "surge"? Why is this timing so important for reproduction? ​ The LH surge triggers ovulation (release of the egg) at the right time for fertilization. What are some methods of birth control? What is the difference between a temporary and a permanent method? Temporary Methods: Condoms, birth control pills, IUDs, etc. Permanent Methods: Sterilization (vasectomy for men, tubal ligation for women). Chapter 27 Learning Outcomes (Study Guide): What are the phases of the prenatal period? Approximately how long is a "full term" pregnancy? Germinal Phase: Fertilization to 2 weeks (formation of the zygote and blastocyst). Embryonic Phase: Weeks 3-8 (development of major organs and body systems). Fetal Phase: Weeks 9-40 (growth and maturation of the organs and systems). ​ Full-Term Pregnancy: Approximately 40 weeks (or about 9 months). What does the term "conceptus" mean? How is this term different from "fetus"? Conceptus: The fertilized egg and its subsequent stages of development, including the embryo and fetus. Fetus: The stage from the 9th week of development until birth, when the major organs are developed and growth occurs. What must happen to a sperm cell before it is able to begin the process of fertilization? Capacitation: The sperm undergoes biochemical changes in the female reproductive tract, including changes to the acrosome, allowing it to penetrate the egg's zona pellucida. What "zones" surrounding an egg cell must a sperm cell go through before being able to fuse with the egg cell? ​ Zona Pellucida: The outer protective layer of the egg. ​ Corona Radiata: A layer of granulosa cells surrounding the zona pellucida that sperm must pass through to reach the egg. What is the acrosomal reaction? What is the cortical reaction? ​ Acrosomal Reaction: The sperm’s acrosome releases enzymes to break down the zona pellucida and allow sperm penetration. ​ Cortical Reaction: The egg releases enzymes that alter the zona pellucida to prevent additional sperm from entering (prevents polyspermy). What is polyspermy, and how is it prevented during fertilization? Why is it so important that polyspermy is prevented? Polyspermy: When more than one sperm fertilizes an egg, leading to an abnormal number of chromosomes. Prevention: The cortical reaction changes the zona pellucida structure, preventing other sperm from entering. Importance: Prevents chromosomal abnormalities and ensures proper fetal development. What happens to the nuclei of the sperm and egg cells during fertilization? The sperm and egg nuclei merge to form a diploid zygote, combining genetic material from both parents. Approximately how long post-ovulation is an egg cell able to be fertilized? An egg can be fertilized within 12-24 hours after ovulation. What is the result of fertilization? Is this one cell or two? Haploid or diploid? Result: A single diploid zygote formed by the fusion of two haploid gametes (sperm and egg). When does the egg cell complete meiosis? The egg completes Meiosis II only after fertilization by a sperm. What are the stages of the pre-embryonic period of human development? What is the process of cleavage, and when does this occur? Stages: 1.​ Zygote: A single fertilized cell. 2.​ Morula: Solid ball of cells (day 3-4). 3.​ Blastocyst: A hollow ball of cells with a fluid-filled cavity (day 5-6). Cleavage: Rapid cell division without growth, occurring from fertilization to the blastocyst stage. Where does a growing conceptus implant in the uterus? How many days post-fertilization does this occur? The blastocyst implants in the endometrium of the uterus, typically around 6-7 days after fertilization. What happens to the embryo during implantation? What happens to the uterine lining? The embryo embeds into the endometrial lining, which undergoes changes to support pregnancy. The uterine lining thickens and becomes more vascular. What signaling maintains the uterine lining if implantation is successful? What releases this signal? Human Chorionic Gonadotropin (hCG) is released by the embryo, signaling the corpus luteum to continue producing progesterone, which maintains the uterine lining. What are the extraembryonic membranes? What is the function of each? Amnion: Surrounds the embryo, providing a protective fluid-filled sac. Chorion: Forms the placenta and connects to the uterus. Yolk Sac: Provides early nutrients and blood cell formation. Allantois: Forms part of the umbilical cord and contributes to early waste removal. What is gastrulation? What are the three primary germ layers? ​ Gastrulation: The process during which the three primary germ layers (ectoderm, mesoderm, and endoderm) are formed. ​ Primary Germ Layers: 1.​ Ectoderm: Develops into skin and nervous system. 2.​ Mesoderm: Develops into muscles, bones, and circulatory system. 3.​ Endoderm: Develops into internal organs (e.g., lungs, digestive system). What is the placenta? What functions occur here? Placenta: An organ that connects the developing fetus to the uterine wall, providing nutrients, oxygen, and removing waste. Functions: Nutrient exchange, hormone production, immune protection, and waste removal. What does the placental barrier consist of? What substances can cross this barrier? Which cannot?  ​ The placental barrier consists of the membranes separating maternal and fetal blood. ​ Substances that can cross: Oxygen, nutrients, waste, and some hormones. ​ Substances that cannot cross: Large molecules (e.g., red blood cells) and most drugs. What does the term organogenesis refer to? When during development does this process take place? ​ Organogenesis: The formation of organs from the three germ layers. ​ Timing: Occurs primarily during weeks 3-8 of pregnancy. What is the umbilical cord? Is the blood flowing through the umbilical arteries oxygen-rich or oxygen-poor? What about the umbilical vein? ​ Umbilical Cord: Contains two umbilical arteries (carrying deoxygenated blood) and one umbilical vein (carrying oxygenated blood to the fetus). ​ Oxygen-rich: Blood in the umbilical vein. ​ Oxygen-poor: Blood in the umbilical arteries. What are three ways that fetal circulation is different from that of a typical adult human? What is the functional reason for these differences? Three Differences: 1.​ Foramen Ovale: A hole between the right and left atria to bypass the lungs. 2.​ Ductus Arteriosus: A vessel that connects the pulmonary artery to the aorta, bypassing the lungs. 3.​ Ductus Venosus: A vessel that shunts blood from the umbilical vein to the inferior vena cava, bypassing the liver. Reason: These adaptations allow oxygenated blood from the placenta to bypass the non-functional fetal lungs and liver. What are some physiological changes that occur during pregnancy? Changes: Increased blood volume, cardiac output, and respiratory rate; hormonal changes (e.g., increased progesterone); weight gain, and increased kidney function. What hormones are involved in the positive feedback loop that stimulates uterine contractions during pregnancy? What is the function of each in this feedback loop? Hormones: ​ Oxytocin: Stimulates uterine contractions. ​ Prostaglandins: Enhance the effect of oxytocin and promote cervical dilation. ​ Function: These hormones work together to increase the intensity and frequency of contractions during labor. What are the three stages of labor? What occurs in each stage? Stage 1: Dilation of the cervix, beginning with contractions and ending with full dilation (10 cm). Stage 2: Expulsion of the fetus (from full dilation to birth). Stage 3: Placental delivery, when the placenta is expelled from the uterus. What conceptual position is most conducive for a vaginal childbirth? The head-down position (cephalic presentation) is most conducive for vaginal childbirth. What hormones are involved in the milk "letdown" reflex? What is the function of each in this feedback loop? Prolactin: Stimulates milk production. Oxytocin: Stimulates milk ejection (letdown). Function: Prolactin ensures milk production, and oxytocin ensures the milk is released from the mammary glands. What is a gene? What is an allele? ​ Gene: A segment of DNA that encodes for a specific trait or protein. ​ Allele: Different forms or variations of a gene. What is a genotype? What does it mean to have a homozygous genotype? What about a heterozygous genotype? ​ Genotype: The genetic makeup of an organism (e.g., BB, Bb, bb). ​ Homozygous: Two identical alleles for a gene (e.g., BB or bb). ​ Heterozygous: Two different alleles for a gene (e.g., Bb). How is a phenotype different from a genotype? How is a phenotype related to a genotype? ​ Phenotype: The physical expression of the genotype (e.g., eye color). ​ Relationship: Genotype determines the phenotype. What is a Punnett square? What two biological processes does it model, and how does it model these? A Punnett square models the inheritance of alleles, showing the potential genetic outcomes of offspring based on parental genotypes. Processes Modeled: Meiosis (for allele separation) and Fertilization (for allele combination). What does it mean for one allele to be completely dominant over the other? How is this typically notated? ​ Complete Dominance: One allele completely masks the effect of the other (e.g., in a dominant-recessive relationship). ​ Notation: Dominant alleles are capitalized (e.g., A), recessive alleles are lowercase (e.g., a). What considerations need to be taken when working with sex-linked traits? How is allelic notation typically handled in this case? Considerations: Sex-linked traits are carried on the X chromosome, so males (XY) are more likely to express recessive traits linked to X because they only have one X chromosome. Allelic Notation: X^A or X^a for X-linked traits, Y carries no allele for these traits. Could you determine the probability of an offspring of a given genotype and/or phenotype given the genotypes of the two parents of the offspring for autosomal alleles? What about sex-linked traits? Yes, Punnett squares can predict the probability of an offspring inheriting specific traits, whether autosomal or sex-linked. If a couple has a 25% probability of producing an offspring with a given trait, does this mean if they have four children, one of them will definitely have the trait?  ​ A 25% chance for a trait means the parents’ genotypes suggest a 1 in 4 likelihood for each child to inherit the trait, but not a guarantee for a specific number of children. What is a polygenic trait? Are most traits polygenic? ​ Polygenic Traits: Traits influenced by multiple genes, e.g., skin color and height. ​ Are Most Traits Polygenic? Yes, many human traits (e.g., intelligence, height, eye color) are polygenic.