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BIOL 67B Final Q's
Terms in this set (18)
Define the terms digestion and absorption, describe how molecules are digested, and indicate which molecules are absorbed.
Digestion: Breakdown of ingested food into smaller structures, there is both mechanical, which is break down via chewing and mixing and there is chemical, which is broken down via enzymes like amylase or trypsin.
Absorption: transport of digested molecules, electrolytes, vitamins, water, etc from the GI tract into blood and lymph.
Carbohydrates are chemically digested into sugars,
proteins are digested into amino acids, and lipids are digested into fatty acids. These are all absorbed into blood or lymph.
Describe the structure and function of the mucosa, submucosa, and muscularis.
. Mucosa: consists of epithelium, also has a lamina propria layer and muscularis mucosae layer. This is the site of secretion and absorption. It is in contact with the lumen and its contents.
Submucosa: this area contains blood vessels lymph vessels and nerves. Has the Meissner's plexus housed here, which is composed of nerves and ganglia that innervate the smooth muscle. Also houses MALT, which prevents ingested microorganisms from crossing the GI tract wall. Also has the Peyer patches, which are nodules of lymph.
Muscularis: has a most inner layer of circular muscle and outer longitudinal layer of muscle. The motility and contraction of the muscularis is regulated by the nerve plexuses like the Myenteric.
Describe the location and composition of the submucosal and myenteric plexuses and explain the actions of autonomic nerves on the gastrointestinal tract.
The myenteric plexus (Auerbach's plexus) and the submucous plexus (Meissner's plexus). The myenteric plexus is situated between the circular muscle layer and the longitudinal muscle layer in the lower esophagus, stomach, and intestines. The submucous plexus, as its name implies, is located in the submucosal tissue, which connects the surface mucous membrane lining to the deeper muscle layers in the stomach and intestines.
The myenteric plexus receives its messages from the vagus nerve and responds by transmitting the message to muscle cells, which are thereby activated to contract. The myenteric plexus stimulates the muscles to contract in peristaltic waves and that it helps keep muscle tone throughout the intestine walls, promotes secretions of intestinal juices, and allows muscular constrictions (sphincters) to open, thus permitting food to pass from one part of the digestive system to another.
The function of the submucous plexus in the stomach is working against the myenteric plexus to control the muscular contractions more finely. In the intestines it is generally believed to work in accord with the myenteric plexus in producing peristaltic waves and increasing digestive secretions.
What are the consequences of blocking the common bile duct with a gallstone?
A blocked bile duct from a gallstone can cause inflammation of the gallbladder known as, cholecystitis. This can result in severe pain, nausea, vomiting and bloating. A treatment for this can be complete removal of the gallbladder. The liver will continue to produce bile, but concentrating bile will now no longer occur with the absence of the gallbladder.
Why is the stomach's wall normally not digested by the acids and digestive enzymes in the lumen?
The stomach has specialized cells that assist in protecting the stomach wall from its acidity. Surface mucosa cells are an example. These cells secrete an alkaline mucous that can help to prevent stomach ulcers. These cells help to protect our stomach lining from becoming harmed and inflamed from the presence of too much acid because of the secretions of HCl from the parietal cells or from the food we ingest. It is important to keep a pH that is acidic so our food can be broken down and move along the digestive tract but not too acidic to the point of causing harm to our stomach and its lining.
Describe the effects of secretin and CCK on the bile ducts and gallbladder.
CCK and secretin stimulate the gallbladder to contract, increasing bile flow into the common bile duct, and the sphincter of Oddi to relax, allowing bile to flow from the common bile duct to the duodenum
List the effects of growth hormone on carbohydrate and lipid metabolism.
Carbohydrate metabolism: growth hormone decreases glucose uptake in tissues such as our skeletal muscle and fat. Has an "insulin resistance" character where it decreases it actions to allow for less glucose uptake. This causes a higher glucose concentration in our blood.
Lipid metabolism: growth hormone causes lipolysis and the release of many fatty acids into our blood and other body fluids. It stimulates the conversion of fatty acids to acetyl co A and uses the acetyl co A as a form of energy.
List the overall responses of muscle, adipose tissue, and liver to insulin. What effects occur when the plasma insulin concentration decreases?
Insulin is the main hormone released during the absorptive state. It is released in response to increased levels of blood glucose. Insulin targets the muscles, adipose tissue, and liver in its effort to maintain glucose levels. It targets the liver and muscle cells to form glycogen, it does this by increasing glycogenesis. It targets adipose tissue to increase the uptake of triglycerides from the blood and to decrease the break down of them. It does this by stimulating lipogenesis and inhibiting lipolysis. The plasma insulin concentration decreases as a result of all of this. This, in turn, causes a decrease of glucose and triglycerides in the blood and an increase in the storage of glycogen and triglycerides in our tissues.
Distinguish between the roles of glycerol and free fatty acids during fasting.
During fasting, there is adipocytes which can hydrolyze trigylcerides in our body and turn them into fatty acids and glycerol through the process of lipolysis. Hydrolyzing the trigylcerides to become fatty acids and glycerol are essential during fasting as it can then be converted into ATP and used for energy. We may not be obtaining energy during fasting periods due to no uptake of food or nutrients for fast acting energy to our body. So, lipolysis is needed to convert these fats we already have to make up for it.
Describe the synthesis and release of gonadotrophin-releasing hormone (GnRH) and how it works in the anterior pituitary.
GnRH is a hormone released from the hypothalamus. It reaches specific endocrine cells on the anterior pituitary via the hypophyseal portal system. These endocrine cells are stimulated by GnRH to release the two hormones, follicle stimulating hormone, FSH and luteinizing hormone, LH. The stimulation of GnRH for the first time in the body and inevitable release of FSH and LH, initiates puberty in both males and females.
Describe the synthesis and release of follicle-stimulating hormone (FSH) and leutienizing hormone (LH) from the anterior pituitary.
FSH and LH are stimulated by GnRH from the hypothalamus. GnRH travels to the anterior pituitary where FSH and LH reside in endocrine cells via the hypophyseal portal system. FSH and LH are then released and target the gonads of both the female and males. The gonads will produce sex hormones and initiate the processes of gamete maturation. In females, FSH specifically stimulates the development of the ovarian follicles. LH is more focused on stimulating ovulation. When the ovulation phase begins in the ovarian cycle, is it due to a huge spike in the release of LH.
Describe the effects of castration on FSH and LH secretion in the male. Explain the experimental evidence suggesting that the testes produce a polypeptide that specifically inhibits FSH secretion
Castration increases LH/FSH secretion by eliminating negative feedback from sex hormones that are produced by the testes. Evidence that suggests that the testes produce a polypeptide that specifically inhibits FSH secretion was done by injecting testosterone into castrated animals. This resulted in a return of their FSH levels to how they were before they were casturated. Seminiferous tubules within the testes also contain sustentacular cells which can release inhibin when the sperm cell count gets really high. Inhibin works to decrease FSH secretion.
Describe the two compartments of the testes with respect to (a) structure, (b) function, and (c) response to gonadotropin stimulation. Describe two ways in which these compartments interact.
The two compartments of the testis are the seminiferous tubules and the interstitial fluid, which resides in the spaces between the tubules.
The seminiferous tubules contain a lumen and are made of connective tissue. They house two types of cells, sertoli cells and a form of germ cells. Sertoli cells aid in nourishing and developing sperm and can release inhibin, to inhibit the release of FSH to maintain a normal count of sperm. The germ cells develop into sperm continuously once puberty begins. The sertoli cells also form the blood-testis barrier, which protects the sperm from particles in our blood.
Interstitial fluid surrounds the tubules. In this fluid is interstitial cells that are stimulated by LH to produce androgens, the most common being testosterone. This is where the majority of androgens are released in males.
Compare the structure and contents of a primary follicle, secondary follicle and graafian follicle.
Primary Follicle: contains a primary oocyte with a single layer of granulosa cells. In between the oocyte and the granulosa cells is the zona pellucida. This follicle secretes estrogen as it goes along maturation.
Secondary Follicle: contains a primary oocyte with multiple layers of granulosa cells. This follicle also contains thecal cells which secretes androgens like estrogen with the help of the granulosa cells.
Graafian Follicle: This is also known as a mature follicle. This contains a secondary oocyte which is surrounded by a zona pellucida and corona radiata. It has multiple layers of granulosa cells and a fluid-filled antrum, surrounding the oocyte.
Explain how administration of glucocorticoids to a pregnant woman would treat congenital adrenal hyperplasia in her fetus.
Glucocorticoids can treat congenital adrenal hyperplasia in the fetus as it is able to suppress adrenal androgen production and works to prevent adrenal insufficiency, which is also known as Addison's disease. Congenital adrenal hyperplasia causes a deficiency of glucocorticoids in the body so the increase in taking of glucocorticoids makes up for the loss. Glucocorticoids will decrease the release of adrenocorticotropic hormone, which functions to release adrenal androgens. They are trying to stop this release.
List the functions of the Sertoli cells.
Sertoli cells reside in the seminiferous tubules in the testis of the male. Sertoli cells protect the sperm and nourish them through their development. They can also release the hormone, inhibin, when the amount of sperm is getting too high. This inhibits the secretion of FSH. We have many Sertoli cells in the tubules and they can form a tight barrier known as the blood-testis barrier. This barrier helps to protect the sperm from the components of our blood as well as our leukocytes. The leukocytes may detect the sperm as a foreign material, this barrier prevents any destruction of sperm and keeps it intact and safe.
What are the feedback controls from the testes to the hypothalamus and pituitary?
First, the hypothalamus begins the formation of sperm via the secretion of GnRH which triggers the anterior pituitary to release LH and FSH. FSH and LH target the testes to begin spermatogenesis and release testosterone. The high increase of testosterone supports spermatogenesis and its production but inhibits GnRH and the release of FSH and LH as much. This is an example of a negative feedback system. On top of the high testosterone levels, the release of inhibin by the sertoli cells is an addition to the negative feedback control as it also inhibits specifically FSH secretion.
Describe the various stages from oogonium to mature ovum.
The process of oogenesis is the maturing of a primary oocyte into a secondary oocyte. While in the womb, the ovary of the fetus contains primordial germ cells called oogonias. They complete mitosis and form primary oocytes. They begin the process of meiosis but become arrested in prophase 1 until the time of puberty. Once puberty begins, this is the start of the ovarian cycle and completing oogenesis. The first phase is the follicular phase, where the primary oocyte completes meiosis 1 and form 2 cells. One does not continue develop and the other becomes a secondary oocyte and reaches metaphase II, where it is then arrested again. If the oocyte becomes fertilized during ovulation, then it will complete the entirety of meiosis II and become a mature ovum.
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