ZOO 332 Final

Gamete formation in both sexes involves meiosis, a unique kind of nuclear division that, for the most part, occurs only in the gonads. Mitosis (the process by which most body cells divide) distributes replicated chromosomes equally between the two daughter cells. Consequently, each daughter cell receives a full set of chromosomes identical to that of the mother cell. On the other hand, Meiosis consists of two consecutive nuclear divisions ( that follow one round of DNA replication. Its product is four daughter cells instead of two, each with half as many chromosomes as typical body cells. Meiosis reduces the chromosomal number by half (from 2n to n) in gametes. Also, it introduces genetic variation because each of the haploid daughter cells have only some of the genes of each parent. Meiosis I reduces the chromosome number from 2n to n. Prophase of Meiosis I is the only stage where the replicated chromosomes seek out their homologous partners and pair up with them like buttoning, this is called Synapsis and little groups of four chromatids called Tetrads are formed. During Synapsis, Crossovers or Chiasmata are formed within each tetrad as the free ends of one maternal and one paternal chromatid wrap around each other and allow an exchange of genetic material between the paired chromosomes. Meiosis II mirrors Mitosis in every way except that the chromosomes are not replicated before it begins. Instead, the sister chromatids in the two daughter cells of Meiosis I are simply parceled out among 4 cells. As a result of Meiosis, it is likely that no two gametes are exactly alike, and all are different from the original mother cells.

Define meiosis. Compare and contrast it to mitosis.

1. Ingestion: Taking food into the digestive tract, usually via the mouth. 2. Propulsion: Moves food through the GI tract, includes Swallowing which is initiated voluntarily, and Peristalsis an involuntary process. Peristalsis is the major means of propulsion which involves alternate waves of contraction and relaxation of muscles in the organ walls. It squeezes the food along the tract and does some mixing as well. 3. Mechanical Digestion: Physically prepares food for chemical digestion by Enzymes. Processes include chewing, mixing of food with saliva by the tongue, churning food in the stomach, and Segmentation: rhythmic local constrictions of the small intestine. Mixes food with digestive juices and increases the efficiency of absorption by repeatedly moving different parts of the food mass over the intestinal wall. 4. Chemical Digestion: Series of catabolic steps in which complex food molecules are broken down to their chemical building blocks by enzymes secreted into the lumen of the GI tract. Begins in the mouth and essentially complete in the SI 5. Absorption: The passage of digested end products (plus vitamins, minerals, and water) from the lumen of the GI tract through the mucosal calls by active or passive transport into the blood or lymph. SI is major absorptive site. 6. Defecation: Eliminates indigestible substances from the body via the anus in the form of feces.

Define the major processes involved in digestion

Sex determination is caused by the X and Y chromosomes exchanged during fertilization. It's the male and sperm that determines the sex of the baby. If a X sperm interacts with the X egg, then the baby will be female. If a Y sperm interacts with the X egg, the baby will be male. Sperm and eggs are called Gametes (sex cells that are haploid) that form a Zygote when the sperm fertilizes the egg. The Sex-determining Region of the Y chromosome (SRY) happens during the 7th week of development, the Y chromosome determines the male sex. If you have SRY, you get a male and the formation of testes because of a gene for Testis-determining SRY protein. If you don't have SRY, you get a female and the formation of ovaries. A fetus has bipotential tissues up until 7 wks, could be a male or a female. Gonads are testes or ovaries. If male, antimullerian/mullerian inhibiting hormone will degenerate the Mullerian Duct. Testosterone then promotes Wolffian Duct growth (epididymis, vas deferens, seminal vesicles). DHT is a hormone that is responsible for the external male genitalia and the prostate. If female, the Wolffian Duct will degenerate naturally and the absence of antimullerian hormone will allow the Mullerian Duct to develop (vagina, uterus, oviduct).

Describe how sexual determination occurs in the fetus. Describe the chromosomal and hormonal mechanisms

Liver: Largest gland in the body, main function is to filter and process the nutrient-rich blood delivered to it. Has Hepatocytes which produce bile and that bile gets picked up by the Bile Canaliculi. The hepatocytes also process nutrients, detoxify substances, and store fat soluble vitamins. Gallbladder: Stores bile that is not immediately needed for digestion and concentrates it by absorbing some of its water and ions. When empty or only storing small amounts of bile, its mucosa is thrown into honeycomb-like folds that, like the rugae of the stomach, allow the organ to expand as it fills. Pancreas: Produces enzymes that break down all categories of foodstuffs, which the pancreas then delivers to the duodenum. Have Acini cells that are full of rough ER and have zymogen granules that contain the digestive enzymes they manufacture. Pancreatic juice is made up of bicarbonate, inactive forms of proteases, amylase, lipase, and nuclease. Bile salts are the major stimulus for enhanced bile secretion

Describe the Liver, Gallbladder, and Pancreas

Mucosa: The innermost layer, a moist epithelial membrane that lines the GI tract lumen from mouth to anus. Its major functions are 1. to Secrete mucus, digestive enzymes, and hormones, 2. to Absorb the end products of digestion into the blood, and 3. to Protect against infectious disease. Made of simple columnar epithelium. Submucosa: Areolar connective tissue containing a rich supply of blood and lymphatic vessels, lymphoid follicles, and nerve fibers. Its abundant elastic fibers enable the stomach to regain its normal shape after temporarily storing a large meal. Its extensive vascular network supplies surrounding tissues of the GI tract wall. Muscularis: Responsible for Segmentation and Peristalsis. Typically has an inner circular layer and an outer longitudinal layer of smooth muscle cells. In certain places, the circular layer thickens and forms Sphincters that act as valves to prevent backflow and control food passage from one organ to the next. Serosa: Protective outermost layer, is the visceral peritoneum. Formed of areolar connective tissue covered with mesothelium, a single layer of squamous epithelial cells. In the esophagus, Serosa is replaced by Adventitia (ordinary fibrous connective tissue that binds the esophagus to surrounding structures)

Describe the four layers of the gut including general functions

A healthy digestive system is essential to maintaining life, because it converts food into the raw materials that build and fuel our body's cells. Specifically, the DS takes in food, breaks it down into nutrient molecules, absorbs these molecules into the blood stream, and then rid the body of the indigestible remains.

Describe the functions of the digestive system

The anal canal is the last segment of the large intestine. It begins where the rectum penetrates the levator ani muscle of the pelvic floor and opens to the body exterior at the anus. The anal canal has two sphincters, an involuntary internal anal sphincter composed of smooth muscle, and a voluntary external anal sphincter composed of skeletal muscle. The sphincters, which act rather like purse strings to open and close the anus, are ordinarily closed except during defecation. The Mucosa of the anal canal (stratified squamous) merges with the true skin surrounding the anus and is different than the rest of the colon, reflecting the greater abrasion that this region receives. It hangs in long ridges or folds called Anal Columns. Anal Sinuses, recesses between the anal columns, exude mucous when compressed by feces, which aids in emptying the anal canal.

Describe the gross/microscopic anatomy and basic functions of the Anus

Begins at the back of the pharynx and is about 10 inches long, is collapsed when not involved in food propulsion. Main function is Motility by Peristalsis. Made mostly of Stratified Squamous Epithelium. Layers here are different: Mucosa contains Simple Squamous, Submucosa contains Areolar Connective Tissue, the Muscularis has Longitudinal and Circular layers, and outermost layer is Adventitia.

Describe the gross/microscopic anatomy and basic functions of the Esophagus

Major digestive function is to absorb most of the remaining water from indigestible food residues, stores the residues temporarily, and then eliminate them from the body as semisolid feces. Has the following subdivisions: cecum, appendix, colon, rectum, and anal canal. Have ascending colon, transverse colon, descending colon, and the sigmoid colon. The colon Mucosa is simple columnar epithelium except in the anal canal. Because most food is absorbed before reaching the large intestine, there are no circular folds, no villi, and virtually no cells that secrete digestive enzymes. But the Mucosa is thicker, has crypts and goblet cells in them. The goblet cells produce mucous which eases the passage of feces and protects the intestinal wall from irritating acids and gases released by resident bacteria in the colon.

Describe the gross/microscopic anatomy and basic functions of the Large Intestines

The mouth is the only part of the alimentary canal involved in Ingestion. However, most digestive functions associated with the mouth reflect the activity of the related accessory organs, because food is chewed and mixed with saliva containing enzymes that begin the process of chemical digestion. The mouth also begins the propulsive process of swallowing, which carries food through the pharynx and esophagus to the stomach. Saliva cleanses the mouth, dissolves food chemicals so that they can be tasted, moistens food and aids in compacting it into a bolus, and contains enzymes that begin the chemical breakdown of starchy foods. Also protects the mouth. Contains Amylase that breaks down carbs and fat, NO PROTEIN DIGESTION in the mouth, also has Lysozyme (antibacterial enzyme that helps prevent tooth decay)

Describe the gross/microscopic anatomy and basic functions of the Mouth

From the mouth, food passes into the oropharynx and then the laryngopharynx. Histology of the pharyngeal wall resembles the oral cavity. Contractions of the pharyngeal constrictor muscles propel food into the esophagus below. Main function is Deglutition (swallowing) of Bolus. Swallowing is both voluntary and involuntary. Starts out voluntary with the Esophageal Sphincter contracting to not allow food down into the trachea. Becomes involuntary when that relaxes and food gets pushed down the esophagus (when you can't breathe and swallow at the same time). The Uvula and Hard Palette also rise up while chewing to prevent food from going into Respiratory structures.

Describe the gross/microscopic anatomy and basic functions of the Pharynx

After the sigmoid colon, has three lateral curves or bends represented internally as three transverse folds called Rectal Valves. These valves separate feces from flatus, in other words, they stop feces from being passed along with gas.

Describe the gross/microscopic anatomy and basic functions of the Rectum

The body's major digestive organ (proteins, carbohydrates, and fats) and virtually all absorption occurs here (amino acids, monosaccharides, fat, water, and electrolytes). Also aids in Motility (peristalsis and segmentation) and Secretion (bile, pancreatic juice, hormones). Has 3 parts: Duodenum, Jejunum, and Ileum. Lined with Villi on folds made up columnar epithelium that make absorption more efficient. Have Lacteals for fat absorption.

Describe the gross/microscopic anatomy and basic functions of the Small Intestines

Expandable muscular organ that is a temporary storage tank where chemical breakdown of proteins begins and food is converted to a creamy paste called Chyme. Also does mechanical digestion and controls the movement of chyme to certain areas of the GI tract like the SI. It's pH is 3 so it's highly acidic. Layers are also modified for the stomach like the Mucosa is made of Simple Columnar composed entirely of mucous cells. Has Gastric Pits which lead to tubular Gastric Glands that produce the stomach secretion called Gastric Juice.

Describe the gross/microscopic anatomy and basic functions of the Stomach

Lie in sockets in the gum-covered margins of the mandible and maxilla. Main job is Mastication or chewing where the teeth tear and grind the food, breaking it down into smaller fragments. We have 8 Incisors for cutting or nipping off pieces of food. We have 4 Canines that tear and pierce. We have 8 Premolars and 8 (12 with wisdom teeth) Molars for grinding and crushing.

Describe the gross/microscopic anatomy and basic functions of the Teeth

The female duct system has little or no actual contact with the ovaries. An ovulated oocyte is cast into the peritoneal cavity, and some oocytes are lost there. Uterine/Fallopian Tubes/Oviduct: Form the initial part of the female duct system. Receive the ovulated oocyte and where fertilization usually occurs. Fingerlike projections called Fimbriae capture the oocyte and carry it into the uterine tube. Infundibulum to Ampulla (region where fertilization usually occurs) to Isthmus to Uterus. Oocyte is carried to the uterus by a combo of muscular peristalsis and the beating of the cilia. Uterus: Hollow, thick-walled, muscular organ that functions to receive, retain, and nourish a fertilized ovum. Has a body, fundus (rounded region superior to entrance of uterine tubes), and cervix (narrow neck the projects into vagina). Has cervical glands that produce mucous to block bacteria from entering the uterus. Wall is composed of 3 layers: Perimetrium is the outermost serous layer, Myometrium is the smooth muscle layer that contracts to deliver a baby, and the Endometrium is the mucosal lining that the embryo buries into if there's fertilization. Endometrium has a Basal layer that makes a new Functional layer every month because it leaves during menstruation. Vagina: Thin-walled tube about 8-10 cm long, called the birth canal because it provides a passageway for delivery of an infant and for menstrual flow. Also receives the penis and semen during sexual intercourse, so it is the female copulation organ. pH usually quite acidic to keep it healthy and free of infection, but also hostile to sperm. Virgins have a Hymen (mucosa near distal vaginal orifice that forms an incomplete partition) that is very vascular and may bleed when stretched or ruptured during first intercourse. Vaginal Fornix is up by uterus and c-shaped around cervix.

Describe the location, structure, and function of each of the organs of the female reproductive duct system.

Penis: Copulatory organ designed to deliver sperm into the female reproductive tract. The penis and scrotum which hang suspended from the perineum make up the external genitalia. The penis consists of an attached root and a free shaft or body that ends in an enlarged tip called the glans penis. The skin covering the penis is loose, and it slides distally to form a cuff called the prepuce or foreskin around the glans. The Corpus Spongiosum surrounds the urethra and forms the glans and the bulb of the penis. The Corpora Cavernosa make up most of the penis. Epididymis: Cup shaped and caps the superior aspect of the testis. Have stereocilia that allow them to absorb excess testicular fluid and to pass nutrients to the many sperm stored temporarily in the lumen. Sperm are ejaculated from here. Ductus/Vas Deferens: Runs upward from the epididymis over the bladder and its end expands to form the ampulla. It then joins with the duct of the seminal vesicle to form the short Ejaculatory Duct. Each ejaculatory duct enteres the prostate where it empties into the urethra. At the moment of ejaculation, the thick layers of smooth muscle in the ductus deferens walls create strong peristaltic waves that rapidly squeeze the sperm forward along the tract and into the urethra. Vasectomy is tying off each ductus deferens so the sperm can't reach the body exterior. Form of birth control that is close to 100% Urethra: The terminal portion of the male duct system. Conveys both urine and semen (at different times). Comes from the bladder, through the prostate, and runs through the penis. Its mucosa contains scattered urethral glands that secrete mucus into the lumen just before ejaculation.

Describe the location, structure, and function of the accessory reproductive organs of the male.

The monthly series of events associated with the maturation of an egg. The so-called typical ovarian cycle repeats at intervals of 28 days, with ovulation occurring midcycle. Follicular Phase (Day 1-14): Stage 1. Primordial follicle activated and squamouslike cells around primary oocyte grow, become cuboidal cells and oocyte enlarges, becomes Primary follicle. Stage 2. Follicular cells proliferate, forms stratified epithelium around the oocyte and primary follicle becomes Secondary Follicle, cells become Granulosa cells. Stage 3. Layer of connective tissue condenses around the follicle and forms Theca Folliculi, Thecal cells produce androgens and Granulosa cells convert those to estrogens, oocyte makes transparent extracellular membrane called Zona Pellucida that encapsulates it, secondary follicle becomes Late Secondary Follicle that has fluid filled space between granulosa cells. Stage 4. Fluid between granulosa cells coalesces to form large fluid-filled cavity called the Antrum, large secondary follicle becomes Vesicular Follicle, also forms surrounding capsule of granulosa cells called the Corona Radiata, follicle bulges from the ovary surface. As one of the final events of follicle maturation, the primary oocyte completes Meiosis I to form the secondary oocyte and first polar body. Stage is set for ovulation and granulosa cells tell oocyte to not complete meiosis yet. Ovulation occurs when the ballooning ovary wall ruptures and expels the secondary oocyte still surrounded by its corona radiata into the peritoneal cavity. Luteal Phase (Day 14-28): After ovulation, the ruptured follicle collapses and the antrum fills with clotted blood. The remaining granulosa cells increase in size and along with the internal thecal cells they form an endocrine structure called the Corpus Luteum. It begins to secrete Progesterone and some Estrogen. If pregnancy does not occur, the corpus luteum degenerates in about 10 days and its hormonal output ends, becomes a scar called the Corpus Albicans. If the oocyte is fertilized and pregnancy ensues, the corpus luteum persists until the Placenta is ready to take over its hormone-producing duties in about three months.

Describe the ovarian cycle phases, and relate them to events of oogenesis

Oogenesis is the process of producing the female sex cells or eggs. Takes years to complete and meiosis also occurs in the ovaries like it did in the testes. Fetal: Have 7 million oocytes, starts off by Oogonia (diploid stem cells of the ovaries) multiply by mitosis and then enter a growth phase and lay in nutrient reserves. Gradually oogonia are transformed into Primary Oocytes (2n) and primordial follicles develop around them. The primary oocytes begin the first meotic division, but become "stalled" late in Prophase I and do not complete it. Birth/Puberty: Female has lifetime supply of primary oocytes at birth, 2 million in cortical region of immature ovary. At puberty, only 250,000 oocytes remain. Small number of primary oocytes are activated each month in response to an LH surge midcycle. However only one is "selected" each time to continue Meiosis I, ultimately producing two haploid cells that are quite dissimilar in size. The smaller one is called the First Polar Body, which is excess nuclear material to get rid of chromosomes. It may continue its development and undergo Meiosis II. The larger cell is the Secondary Oocyte (n) that arrests in Metaphase II and is the cell that is ovulated. If the ovulated seconday oocyte is not penetrated by a sperm, it deteriorates. If sperm penetration does happen, the oocyte quickly completes Meiosis II, yielding one large Ovum and a tiny Second Polar Body. End product of Oogenesis is three tiny polar bodies and one large ovum. All of these cells are haploid, but only the ovum is a functional gamete. This is quite different from Spermatogenesis, where the product is four viable gametes (spermatozoa). Most striking difference between male and female meiosis is the error rate. As many as 20% of oocytes but only 3-4% of sperm have the wrong number of chromosomes, a situation that often results from failure of the homologues to separate during meiosis I. It appears that faced with meiotic disruption, meiosis in males grinds to a halt but in females it marches on.

Describe the process of oogenesis and compare it to spermatogenesis.

Ovarian events are much more complex than those occuring in the testes, but the hormonal controls at puberty are similar in the two sexes. GnRH, the pituitary gonadotropins, and in this case ovarian estrogen and progesterone interact to produce the cyclic events occuring in the ovaries. However, in females another hormone plays an important role in stimulating the hypothalamus to release GnRH. The onset of puberty in females is linked to Adiposity and the messenger from fatty tissue to the hypothalamus is Leptin. If blood levels of lipids and leptin are low, puberty is delayed. There is waxing and waning of anterior pituitary gonadotropins and ovarian hormones and negative and positive feedback interactions that regulate ovarian function. 1. GnRH stimulates FSH and LH secretion on day 1 of the cycle. 2. FSH and LH stimulate follicle growth and maturation and estrogen secretion. FSH acts on granulosa cells and LH acts on thecal cells. 3. The rising estrogen levels in the plasma exert Negative Feedback on the hypothalamus and AP, inhibiting FSH and LH release while prodding the pituitary to synthesize and accumulate these gonadotropins. 4. Although the initial small rise in blood-borne estrogen inhibits the hypothalamic-pituitary axis, high estrogen levels have the opposite effect. Once estrogen reaches a critical blood concentration, it briefly exerts Positive Feedback on the brain and AP 5. High estrogen levels cause LH surge around midcycle. 6. LH surge stimulates a lot of events that lead to Ovulation, estrogen declines. 7. Corpus Luteum forms because of the LH surge. Produces progesterone to maintain functional layer if conception occurs 8. Rising progesterone and estrogen levels cause negative feedback and inhibits LH and FSH release. Release of Inhibin by corpus luteum enhances this effect.

Describe the regulation of the ovarian cycle.

Series of cyclic changes that the uterine endometrium goes through each month as it responds to the waxing and waning of ovarian hormones in the blood. These changes are coordinated with the ovarian cycle phases which are dictated by gonadotropins released by the AP. 1. Menstrual Phase (Day 1-5): Uterus sheds all but the deepest part of its endometrium. Ovarian hormones are at their lowest normal levels and gonadotropins are starting to rise. Functional layer of endometrium detaches from the uterine wall, a process that is accompanied by bleeding for 3-5 days. Detached tissue and blood pass out through the vagina as the menstrual flow. By day 5, growing ovarian follicles start to produce more estrogen. 2. Proliferative Phase (Day 6-14): Endometrium rebuilds itself. Basal layer creates new functional layer because of rising estrogen levels in the blood. Cause cervical mucous to thin and form channels that facilitate the passage of sperm into the uterus. Ovulation occurs in the ovary at the end of this phase in response to the LH surge from the AP. 3. Secretory Phase (Day 15-28): Most constant phase timewise. Endometrium prepares for implantation of an embryo, increasing progesterone causes cervical mucous to become viscous again, forms a cervical plug that keeps uterus private from foreign materials if an embryo has begun to implant. Rising progesterone also inhibits LH release. If fertilization doesn't occur, corpus luteum degenerates, progesterone levels fall, functional layer sloughs off and menstrual cycle starts all over again.

Describe the regulation of the uterine/menstrual cycle

The sperm-producing testes or male gonads lie within the scrotum. From the testis, the sperm are delivered to the body exterior through a system of ducts including the epididymis, ductus/vans deferens, ejaculatory duct, and finally the urethra, which opens to the outside at the tip of the penis. The accessory sex glands that empty their secretions into the ducts during ejaculation are the seminal vesicles, prostate, and bulbourethral glands. The testes are located in the scrotum because viable sperm cannot be produced in abundance at core body temperature (37 C). The superficial location of the scrotum, which provides a temperature about 3 C lower, is an essential adaptation. The scrotum is also affected by temperature changes. When it's cold, the testes are pulled closer to the pelvic floor (cremaster muscle) and the warmth of the body wall and the scrotum becomes shorter and heavily wrinkled (dartos muscle), reducing its surface area and increasing its thickness to reduce heat loss. When it's warm, the scrotal skin is flaccid and loose to increase the surface area for cooling and the testes hang lower, away from the body trunk. These changes in scrotal surface area help maintain a fairly constant intrascrotal temperature.

Describe the structure and function of the testes, and explain the importance of their location in the scrotum.

Oral Cavity/Esophagus: Motility by swallowing and chewing, Secretion of saliva from the salivary glands and lipase, Digestion of carbohydrates and little bit of fat, no Absorption here. Stomach: Motility by peristaltic mixing and propulsion, a lot of Secretion (HCl by parietal cells, pepsinogen and gastic lipase by chief cells, mucous and HCO3- by surface mucous cells, gastrin by G cells, Digestion of proteins and fats, Absorption of lipid soluble substances like alcohol and aspirin. Small Intestine: Motility by mixing and propulsion primarily by segmentation, Secretion of mostly enzymes, HCO3- and enzymes by the pancreas, bile by the liver, mucous by goblet cells, and hormones, Digestion of carbohydrates, fats, polypeptides, and nucleic acids, a lot of Absorption (peptides, amino acids, glucose, fructose water, vitamins, ions, fats, minerals) Large Intestine: Motility by segmental mixing and mass movement for propulsion, Secretion of mucous by goblet cells, no Digestion, a lot of Absorption (water, minerals, vitamins, small organic molecules)

Discuss digestion, secretion, absorption, and motility within the GI tract

Hormal regulation of gamete and gonadal hormone production involves interactions between the hypothalamus, anterior pituitary gland, and gonads, a relationship called the Hypothalamic-Pituitary-Gonadal (HPG) Axis. Gonadotropin-Releasing Hormone (GnRH): Released from the Hypothalamus and goes to the Anterior Pituitary. Controls the release of FSH and LH. Follicle-Stimulating Hormone acts on the Sertoli cells and promotes spermatogenesis indirectly by stimulating these cells to release Androgen-Binding Protein (ABP). ABP helps androgens bind to their receptors and keeps concentration of testosterone in the spermatogenic cells high. Luteinizing Hormone acts on the Leydig cells and promotes production of Testosterone. The sertoli cells also release Inhibin, a protein hormone that inhibits the AP release of FSH and the hypothalamus release of GnRH. Happens when testosterone levels are high.

Discuss hormonal regulation of testicular function

Saliva: Parotid, Submandibular, and Sublingual glands in the oral cavity secrete saliva. Largely water and slightly acidic. The intrinsic salivary glands secrete saliva continuously in amounts just sufficient to keep the mouth moist. When food enters, the extrinsic glands are activated and copious amounts of saliva pour out. Controlled primarily by the Parasympathetic NS Pancreatic: Produces hormones that are released into the bloodstream (Insulin and Glucagon). Also release digestic juices and Bicarbonate (released by pancreatic epithelial cells). Juices are Proteases (break down proteins), Nucleases (break down nucleic acids), Amylase (breakdown starch), Lipase (break down fats). All of these juices are released as their inactive forms. Acini cells release the digestive juices. Bile: Secreted in the liver by the Hepatocypes. Is alkaline in nature, has bile salts, some billirubin, triglycerides, cholesterol. Function is to Mullcify Fat. Flows in the opposite direction of blood. Gallbladder stores bile until needed and concentrates it. Major vehicle for cholesterol excretion from the body

Discuss the digestive secretions: saliva, pancreatic, bile

1. Cephalic Phase: Occurs before food enters the stomach. Triggered by aroma/taste/sight/thought of food, gets the stomach ready for upcoming digestion. Occurs only when we like or want the food. Goes from Hypothalamus to Medulla Oblongata to the Vagus Nerves to the Parasympathetic Enteric (own NS in the gut) to the Stomach Glands. Acts on salivary glands, stomach, intestine, and glandular organs. Can be suppressed. Stomach secretions begin here. 2. Gastric Phase: Once food reaches the stomach. Most important stimuli are distension, peptides, and low acidity (higher pH). Gastrin secreted by the G cells play a big role in stimulating stomach gland secretion during this phase. Gastrin breaks down proteins and makes chyme, also tells Parietal cells to make more HCl. Inhibited if proteins are digested, pH drops, so G-cells don't secrete. Negative feedback mechanism helps maintain optimal pH and working conditions for the gastric enzymes. 3. Intestinal Phase: Excitatory aspect is when chyme enters the SI, stimulates intestinal mucosal cells to release Gastrin which encourages glands to continue secreting. Inhibitory aspect helps modulate activity going on in the SI. Inhibits acid production, slows gastric emptying, and stimulates bicarbonate production in the pancreas. Protects the SI from excessive acidity and matches the SI's processing abilities to the amount of chume entering it at a given time.

Discuss the phases of gastric secretions

Testosterone not only prompts spermatogenesis but also has multiple anabolic effects throughout the body. It targets Accessory reproductive organs (ducts, glands, and the penis) causing them to grow and assume adult size and function. In adult males, normal plasma levels of testosterone maintain these organs. Male secondary sex characteristics (features induced in the nonreproductive organs by the male sex hormones, mainly testosterone) also make their appearance at puberty. These include pubic/axillary/facial hair, enhanced hair growth on the chest or other body areas, and a deeping of the voice as the larynx enlarges. The skin thickens and becomes oilier, bones grow and increase in density, and skeletal muscles increase in size and mass. The Somatic effects of testosterone are the epiphyseal plate closure and termination of skeletal growth in height occurs in response to rising estrogen levels late in puberty in both boys and girls. Testosterone also boosts basal metabolic rate and influences behavior, and is the basis of the sex drive in males. In embryos, the presence of testosterone masculinizes the brain, and it also appears to continue to shape certain regions of the male brain well into adult life. Testosterone production by the testes supports male reproductive function.

Discuss the physiological effects of testosterone on male reproductive anatomy.

GI tract: Also called alimentary (nourish) canal, it is a continuous muscular digestive tube that winds through the body. It digests food, breaks it down into smaller fragments, and absorbs the digested fragments through its lining into the blood. The organs are the Mouth, Pharynx, Esophagus, Stomach, Small Intestine, and Large Intestine. The LI leads to the terminal opening, or Anus. Food material in the GI tract is technically outside the body because the canal is open to the external environment at both ends. Accessory Organs: Teeth, Tongue, Gallbladder, Salivary glands, Liver, and Pancreas. The teeth and tongue are in the oral cavity while the digestive glands and gallbladder lie outside the GI tract and connect to it by ducts. These organs produce a variety of secretions that contribute to the breakdown of foodstuffs.

Distinguish between the GI tract and the accessory organs

Peristalsis: Progressive, wavelike contractions that move foodstuffs through the alimentary tube organs. Like squeezing a tube. Occurs in the esophagus, stomach, small intestine, and large intestine. Segmentation: Nonadjacent segments of alimentary tract organs alternately contract and relax, moving the food forward then backward. Food mixing and slow food propulsion occurs. Mixes food with digestive juices and increases the efficiency of absorption by repeatedly moving different parts of the food mass over the intestinal wall. Occurs in the small intestine.

Explain peristaltic and segmental contractions in the GI tract

The menstrual and proliferative phases of the uterine cycle overlap the follicular phase and ovulation in the ovarian cycle, and the uterine secretory phase corresponds to the ovarian luteal phase.

How do the ovarian and uterine cycles fit together?

Circular Folds: Deep permanent folds of the mucosa and submucosa. Nearly 1 cm tall, these folds force chyme to spiral through the lumen, slowing its movement and allowing time for full nutrient absorption. Villi: Fingerlike projections of the mucosa, over 1 mm high, give it a velvety texture. The epithelial cells of the villi are chiefly absorptive columnar cells. In the core of each villus is a dense capillary bed and a wide lymph capillary called a Lacteal. Digested foodstuffs are absorbed through the epithelial cells into both the capillary blood and the lacteal. The Villi are large and leaflike in the duodenum and gradually narrow and shorten along the length of the SI. A "slip" of smooth muscle in the villus core allows it to alternately shorten and lengthen. These pulsations increase the contact between the villus and the contents of the intestinal lumen making absorption more efficient, and "milk" lymph along through the lacteals. Microvilli: Exceptionally long densely packed in the absorptive cells of the mucosa, give the mucosal surface a fuzzy appearance called the Brush Border. The plasma membranes of the microvilli bear enzymes called brush border enzymes which complete the digestion of carbohydrates and proteins in the SI

Identify and describe structural modifications of the wall of the small intestine that enhance the digestive process.

1. Mucous Neck Cells: Found in the upper "neck" regions of the glands. Produce a thin, soluble mucus different than the mucous cells of the surface of epithelium. Tonic secretion with irritation of mucosa. Provides a physical barrier between lumen and epithelium. Also secretes Bicarbonate to bring pH back up. 2. Parietal Cells: Found in the middle region of the gastric glands. Simultaneously secrete Hydrochloric Acid (HCl) and Intrinsic Factor. The HCl activates Pepsin which denatures proteins, amylase, and kills pathogens. Intrinsic Factor is needed for Vitamin B12 reabsorption in the SI. 3. Chief Cells: Occur mainly in the basal regions of the gastric glands. Produce Pepsinogen, the inactive form of the protein-digesting enzyme Pepsin. The activation of the Pepsinogen release is stimulated by the HCl from the Parietal cells. The chief cells also secrete Lipase, a fat-digesting enzyme.

Name the cell types responsible for secreting the various components of gastric juice and indicate the importance of each component in stomach activity.

Spermatogenesis is the sequence of events in the seminiferous tubules of the testes that produces male gametes, sperm or spermatozoa. The process begins around age 14 and continues throughout life. A healthy adult male makes about 400 million sperm a day! Start out at the basement membrane with stem cells called Spermatogonia. Each mitotic division of a spermatogonium results in two types of daughter cells-A and B. Type A remains at the basal lamina to maintain the germ cell line, and Type B gets pushed toward the lumen, where it becomes a Primary Spermatocyte (2n) destined to produce 4 sperm. Each primary spermatocyte goes through Meiosis I and forms two smaller haploid cells called Secondary Spermatocytes (n). The secondary spermatocytes continue on rapidly into Meiosis II and their daughter cells are Spermatids (n). These then go through Spermiogenesis and differentiate into Spermatozoa. The Seminiferous Tubules have Sertoli/Sustenacular cells that nourish the developing spermatids and secrete fluids into the lumen. They also promote cell division of spermatids. The Blood-Testis Barrier is made of tight junctions that protect the spermatids from the immune system and phagocytize defective developing cells. The Leydig Cells are found in the interstitial area and are producers of Testosterone

Outline events of spermatogenesis.