BIOL 252 1st Edition Lecture 24 Outline of Last Lecture I. PCT: Tubular ReabsorptionII. Tubular SecretionIII. Loop of HenleIV. Distal Convoluted Tubule and Collecting DuctV. What about the loop?VI. Urine Storage and EliminationVII. Digestive SystemVIII. Saliva and Salivary GlandsIX. Layers of Digestive TractX. PeristalsisXI. StomachOutline of Current LectureI. Digestive SystemII. Reproductive SystemCurrent LectureI. Digestive Systema. Gastric Motilityi. Stomach controls its own motility but may be influenced by vagus nerveii. Emetic center of medulla can cause reverse peristalsis via vagus nerveb. Liveri. Hepatocytes:1. Absorb from the blooda. Glucose, amino acids, iron, vitamins, other nutrients for metabolism or storageb. What do we do with glucose? Make glycogenc. Vein: carrying deoxygenated blood (has already exchanged w/ digestive tract – cannot deliver O2 to liver); so we must have an artery = vein and artery in same direction2. Degrade from blooda. Hormones, toxins, bile pigments, drugs3. Secrete into bloodThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.a. Glucose, albumin, lipoproteins, clotting factors, angiotensinogen, other products4. Excrete bilea. Bile pigments, bile salts c. Circulatory Routesi. Portal system where left capillary bed = liver; right capillary bed = ii. Middle vessel = hepatic portal vein d. Gallbladderi. Bile salts mix w/ fats and emulsify = makes them water soluble ii. Liver secretes about 500 – 1000 mL of bile daily; 80% of bile salts are reabsorbed in small intestineiii. Gall bladder stores and concentrates bile:1. Bilirubin – excretory product2. Bile salts (acids) – steroids synthesized from cholesterol e. Pancreasi. Stomach’s chyme is acidic; pancreatic juice neutralizes (contains HCO3-)ii. Proteases (trypsinogen and carboxypeptidase)iii. Lipaseiv. Amylasev. Ribonuclease and deoxyribonuclease vi. Pancreatic zymogens (proenzymes) are converted to active enzymes in duodenum vii. Nervous system stimulates enzyme release1. ACh from vagus and enteric nerves stimulates enzymatic secretion2. Increased enzymes viii. CCK stimulates enzyme release (and gall bladder contraction)1. CCK secreted by duodenum in response to fatsix. Secretin stimulates bicarbonate release1. Secretin secreted by duodenum in response to acidic chyme f. Small Intestine: duodenumi. Receives stomach contents, pancreatic juice, bileii. Stomach acid is neutralized hereiii. Fats are physically broken up by bile acidsiv. Pancreatic enzymes take over job of chemical digestiong. Jejunumi. First 40% of small intestinesii. Thick muscular walliii. Internal ridges of mucosa: plica 1. Villi2. Microvilli 3. Expand amount of surface area presentiv. If inside were smooth, far less surface area v. Why care about surface area? – Absorptionh. Ileumi. Thinner, less muscular, less vascular than iliumii. Peyer patches: prominent lymphatic nodules i. Microscopic Anatomyi. Blue vein – to liverii. Brush border completes chemical digestion in intestinesiii. Lacteal: where fats go (large molecules) j. Intestinal Motilityi. Peristalsis: gradual movement of contents towards colonii. Segmentation: pinching off of segment, followed by churning w/in segmentk. Large Intestinesi. Most of digestion completeii. Water being pulled out of what’s left iii. What’s in feces?1. Water, solids, bacteria, undigested fiber, fat; remaining: mucus, sloughed epithelial cellsa. What is fiber? Indigestible iv. Large intestine reabsorbs water and electrolytes (compaction) v. Bacterial flora1. Huge colonies of bacteria2. Benefit from our indigestibles – metabolize them and make by productsa. Ferment undigested carbs; helps in synthesis of vitamins B and K3. About 800 species of bacteria populate large intestine l. Defecation Reflexi. Stimulus = rectal wall stretchingii. Involuntary response = contraction of smooth muscle in walliii. Sense of urgency -> internal anal sphincter relaxes (involuntary) iv. Brain tells spinal cord to relax/not relax external anal sphincter (voluntary) v. Steps 1-3 happen automaticallyII. Reproductive Systema. How do two cells form 1 cell with 23 pairs of chromosomes? b. Meiosis:i. Reduces chromosomes number by halfii. Maintains chromosome number for species (at fertilization)iii. Provides genetic diversity (through independent assortment and crossing over)c. Spermatogenesisi. Events of meiosis that are male specificii. Diploid cell (2n) => haploid (n)iii. 23 pairs of chromosomes => 23 unpaired chromosomesiv. Where do cells come from?1. Primordial germ cells from yolk sac migrate to colonize gonads andbecome spermatogonia (or oogonia) 2. Gonia means seedv. Mitosis: Spermatogonium => primary spermatocyte + Spermatogonium1. Constantly spinning off daughter cells vi. Meiosis I: primary spermatocyte => secondary spermatocyte 1. Replicate DNA before we divide2. Start out diploid; before dividing, duplicate; then divide 3. Replication and first division = meiosis Ivii. Meiosis II: second division1. Secondary spermatocyte => 2 spermatids (contain 23 unpaired chromosomes)2. 2 secondary spermatocytes => 4 spermatidsviii. Spermiogenesis1. To make sperm cell, must differentiate the cell2. **Spermatogenesis contains spermiogenesis ix. Where does this happen?1. Inside testes, groups of tubules called seminiferous tubules2. Cells that are spermatogonium are on top, as become sperm – go toward lumen (bottom)x. Spermiogenesis 1. Round looking cell => sperm cell2. Appearance of acrosomal vesicle and flagellum in spermatid3. Growth of acrosome and flagellum4. Shedding of excess cytoplasm5. Mature sperma. Midpiece: mitochondria -> produce ATP to move flagellum b. Nucleusc. Acrosome: specialization, internal membrane that produced in differentiation process that produces enzymesthat helps sperm break barriers to egg6. Spermatozoona. Axoneme’s 9+2 arrangement of microtubulesd. What determines sex?i. SRY gene carried on Y chromosome determines male sex; without it, a female will develope. Semeni. Typical ejaculation is 2-5 mL semen containing1. 10% sperm and spermatic duct secretions2. 30% prostatic fluid3. 60% seminal vesicle fluidii. Sperm count of 50-120 million sperm/mL is typical iii. Seminal fluid: fructose, prostaglandins, prosemenogeliniv. Prostatic fluid: citrate (buffer), enzymes f. Male Hormonal Controli. GnRH: from hypothalamus (responds to environmental stimulus)ii. FSH and LH