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163 Cards in this Set
- Front
- Back
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Small Intestine |
It extends from the pyloric sphincter of stomach to beginning of Lg intestine. It is a tube that carries chyme away from the stomach into Lg intestine. The pyloric sphincter lets chyme out into the duodenum. Sm intestine consists of 3 parts: 1. Duodenum 2. Jejunum 3. Ileum In animals that dont need alot of fermentation for energy nd nutrition, Sm intestine is main site for digestion and absorption. |
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Sm Intestine Structures |
Sm intestines are suspended from body wall by the mesentery. |
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Duodenum |
First portion of sm intestine. It receives chyme as it exits the stomach through pyloric sphincter. |
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Jejunum |
The longest part of Sm intestine, forming a mass of many coils and loops that occupy the ventral abdominal cavity. The bulk of chemical digestion and absorption occur in the jejunum. Mesentery allows sm intestine to have great range of motion. |
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Ileum |
Sm intestine ends at the ileum. Ileum empties into the Lg intestine at the cecum in the horse - at the colon in the dog and cat - at the cucum and colon in the ruminant and pig. Peyers patches, which are aggregates of lymphoid tissue are found prominently in the ileum to help protect animals from disease, work as antibodies, and filtrate fluid. - Cecum is important in herbivores because microbes help breakdown plants. |
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Small Intestine Motility |
The two primary movements in Sm intestine are: 1. Peristalsis 2. Segmentation |
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Peristalsis |
It propels the intestinal contents toward the Lg intestine. |
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Segmentation |
The presence of chyme stretches the intestinal wall, triggering the ring of circular muscle to contract; as one set of contraction relaxes, another are of circular muscle contract in a diff area. These random, localized contractions of circular muscle layer help mix the digestive contents and move the digestive fluid closer to the surface of intestine, increasing its contact w/ mucosal enzymes and absorptive surfaces. It is a mixing action and does not move chyme toward Lg intestine. |
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Sm Intestine Surface Area |
- Sm intestine is long and consists of many loops and coils. - Mucosa lining the Sm intestine is thrown into fold or plications, which are permanent structures (do not stretch) like stomach rugae. - Intestinal mucosa is made of simple columnar epithelial cells that have fingerlike projections called villi, which in turn contain smaller projections called microvilli. - Microvilli form the brush border that provide majority surface area of Sm intestine. |
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Brush Border |
Embedded in brush border are brush border enzymes that are responsible for membranous digestion. Membranous digestion in Sm intestine plays the ultimate role in the digestion of carbohydrates, proteins, and nucleotides. |
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Intestinal crypts |
These undifferentiated cells are the only intestinal cells undergoing cell division and they replace those further up on the tips of the villi as they are lost due to wear. They are located between adjacent villi. |
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Sm Intestine Capillaries |
An extensive network of blood capillaries is found inside the villi. These capillaries collect some of the nutrients absorbed from the G.I tract and transport them to the liver. |
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Lacteals |
Lymphatic capillaries called lacteals also are found in the villi. Lipids are too large to enter the blood capillaries and must be transported in the lacteal. The lacteal carries absorbed lipids and fat substances to the thoracic duct, which empties into the venous blood of the vena cava. |
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The Large Intestine |
The end of the small intestine, the ileum, leads into the Lg intestine, which consist of: 1. Cecum 2. Colon 3. Rectum 4. Anus |
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Lg Intestine Structure |
Overall has a wider diameter than Sm intestine. The amount of microbial fermentation that occurs within Lg intestine contributes to how extensive and complex its anatomy is. Whether the ileum opens into the colon, cecum, or both depends on the species. |
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The Cecum |
Is a blind diverticulum at the beginning of the colon. It varies from being small and inconspicuous in the carnivore, where little fermentation is required, to a voluminous and expansive cecum in equine species that rely heavily on hidgut microbial fermentation. In the horse, the comma shaped cecum is so big it takes up a Lg portion of the abdomen. The cecum in the ruminant is a Lg blind tube. (Herbivores) |
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Segmentation in the Colon & Cecum |
In the colon and cecum of the horse and pig, both the longitudinal muscle, which runs in bands called teniae, and the circular muscle contract, forming bulging saclike structures called sacculations. |
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Sacculations aka haustra |
Certain areas contract then relax, then diff. areas contract and relax in another location. The sacculations are semipermanent and may even be visible post mortem. Sacculations prolong the time during which the contents stay in Lg intestine by creating extra volume. This allows more time for absorption and microbial digestion. |
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Motility of Lg Intestine |
Intestinal contents (Ingesta) travel slowly in the Lg intestine, especially in animals such as the horse and rabbit that require extensive hindgut fermentation to provide energy. The ingesta must be thoroughly mixed to allow contact w/ the absorptive surface of the colon, where absorption of water and ions occurs. Diff. types of motility pattern occur in Lg intestine w/ function of mixing, retaining, propelling ingesta toward the anus. It varies among species, but similar patterns consist of: 1. Segmentation 2. Peristalsis 3. Anti Peristalsis 4. Mass movement (Poop) |
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Segmentation in Lg intestine |
The most common type of movement in the cecum and colon. Segmental contractions move the ingesta back and forth, increasing contact between ingesta and epithelial surface. |
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Antiperistalsis |
Occurs in the opposite direction, toward the stomach. The movement helps slow down the transit of the ingesta, allowing more time for reabsorption to accur. |
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Digestion & Absorption in Lg Intestine |
Two very important functions of Lg intestine are absorption of water and ions, and completion of carbohydrate or protein microbial digestion and absorption. Forestomachs in the ruminant are the primary location of microbial digestion, whereas in nonruminant hindgut fermenting herbivores, such as horses and rabbits, microbial digestion occurs mainly in the cecum and colon. The horses fermentation center, is in the hindgut positioned after the stomach. |
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Emptying the Rectum |
When chyme (ingesta) passes through the Lg intestine much of the water is absorbed, leaving a semisolid material called feces. When feces are transported to the rectum sensory receptors are stimulated. This initiates the defecation reflex that causes the colon and rectum to contract, and relaxes the inner anal sphincter muscle (smooth muscle). The animal perceives the need to defecate. Some species like dog and cat can be trained to close the voluntary outer anal sphincter (skeletal muscle) and delay defecation. Ruminants, horses, birds cant control voluntary sphincter. |
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Pancreas |
It has both endocrine and exocrine functions. It runs right alongside the descending duodenum |
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Endocrine |
It produces various hormones and deposits them directly into the bloodstream. It contains pancreatic islets which contain several diff. cell types and each cell type produces its own hormone. - Beta cells secrete insulin needed to transport glucose into most cells to lower glucose in blood. |
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Exocrine |
It produces digestive proenzymes that are deposited through a duct into the duodenum. It consists of groups of acini. Acinus is made up of single layer columar epithelial which resemble a cluster of grapes surrounding a lumen. The cells of the acini release their secretion into the lumen, which merge with other lumina to form ducts that eventually converge into the pancreatic duct. Pancreatic duct empties into the duodenum. The secretion of the exocrine pancreas contain bicarbonate and pancreatic digestive enzymes. (proenzymes). |
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The Liver |
Secretions are essential for digestion nd absorption of nutrients. It has multitude of other functions not related to digestion. It is the Lg digestive gland in the body. The mammalian liver consists of lobes. It processes the blood leaving the GI tract, preventing toxins from entering the general circulation. It is outside the lumen of the G.I Tract. |
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Liver Productions |
It synthesizes nutrients nd regulating their release into the bloodstream, excreting toxic substances, those that originated within the body and those that have been brought into the body, and producing most of the plasma proteins, cholesterol and many blood coagulation. |
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The gallbladder |
It concentrates and stores bile until it is needed. Some animals eat twice a day so it stores bile until it is needed. When fats are consumed a large quantity of bile enter the duodenum. It also provides the liver w/ storage container so it can continue to excrete waste products through bile production even when animal is not eating. Bile helps digest fat. Horses do not have gallbladders. |
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Liver Bloodstream |
The liver receives blood from two sources: 1. hepatic portal vein from the GI tract (Nutrient rich blood) 2. hepatic artery, a branch of the celiac artery. (oxygen rich blood) |
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Hepatic Artery |
The celiac artery branches directly off the abdominal aorta and supplies oxygenated blood to the liver tissue. |
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Triads |
Both the hepatic artery and the hepatic portal vein enter the liver near the peiphery of the lobules, in area known as triads, so called because the bile ducts also are found there in addition to the hepatic artery and hepatic portal vein. |
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Sinusoids |
The hepatic artery and the hepatic portal vein travel from the periphery of the lobule toward its interior, coming together and emptying their blood into sinusoids, which are large capillaries of the liver. |
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Kupffer Cells |
Attached to the inner surface of the sinusoids are macrophages called kupffer cells, which engulf foreign substances. |
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Central Vein |
Blood from the sinusoids enters the central vein (the middle) which is located at the center of each lobule, and exits the liver returning back to the general circulation via the hepatic vein |
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Canaliculi |
Located between the individual hepatocytes are bile ductules called bile canaliculi |
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Hepatocytes |
Adjacent to the sinusoids are hepatocytes, which come in close contact with the blood |
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Bile |
Bile is excreted from the hepatocytes into these canaliculi and travel the opposite direction from the blood, away from the central vein, emptying into Lg bile ductules, and ultimately into the bile duct at the triad. Bile is necessary for lipid (fat) digestion in the intestines. |
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Common bile duct |
Bile exists in the liver and travels through hepatic ducts emptying into the common bile duct. The cystic duct also comes off the common bile duct. The common bile duct empties directly into the duodenum, but in some species it comes at the pancreas before. |
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Sphincter of Oddi |
It controls the entrance of the bile duct into the duodenum. When the sphincter of Oddi is closed, bile back up into the gallbladder |
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Amylase |
Chemical digestion begins in saliva, mainly in omnivores and not in carnivores. This starch digesting enzyme amylase assists in breakdown of starchy (plant) carbohydrates. Minimal digestion occurs there because |
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Gastric Enzymes |
Gastric pits in the glandular region of the fundus and the body of the stomach contain diff. types of glandular cells like: - Mucous neck cells = make mucuous - Chief Cells = make pepsinogen - G Cells = make hormone called gastrin and secrete it into bloodstream - Parietal Cells = make Hydrochloric Acid (HCI) |
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Parietal Cells |
They are gastric glands that secrete hydrogen and chloride, which form hydrochloric acid (HCI) in the lumen of the stomach. HCI is used to break food down into smaller molecules to be absorbed. They also secrete intrinsic factor, necessary for absorption of vitamon B12 in sm intestine. |
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Mucous Neck Cells |
They secrete a thinner, less viscous, mucus than the surface mucous cells. They are able to divide and create new cells. The new cells can migrate either up into the mucosal surface or further down into the gastric glands to become parietal or chief cells. |
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Chief Cells |
They secrete pepsinogen. Pepsinogen is an inactive precursor form of the enzyme pepsin. It is converted into pepsin by the acidic environment of the stomach created by (HCI). |
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Pepsin |
It is a proteolytic enzyme that begins the chemical digestion of proteins. Once pepsinogen is activated into pepsin it can also activate other pepsinogen molecules. |
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Proteolytic |
Secretion of proteolytic proenzymes such as pepsinogen is essential in the digestive process because constant presence of the active enzyme pepsin would lead to the breakdown of the very cell that is making it. |
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Pyloric sphicter |
Stomach narrows into the pyloric canal terminating at the pylorus, which open into the duodenum through a circular muscle called the pyloric sphincter. The sphincter helps determine the rate of gastric emptying |
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G Cells |
Endocrine cells that secrete the hormone gastrin into the bloodstream. This hormone stimulates parietel cells to produce more HCI |
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Stimulation of Secretion |
3 substances: 1. Acetylcholine = secreted by cholinergic neuron (nervous system) 2. Gastrin = secreted by G Cells (Harmone) 3. Histamine = secreted by ECL Cells (Harmone) Stimulate secretions by glandular cells in the stomach. Make more Hydrochloric Acid (HCI) |
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Acetylcholine (Nervous System) |
Stimulates chief cells (pepsinogen) and parietal cells (HCI). Pancreatic cells have surface receptors that are stimulated by acetylcholine, cck, and secretin. During cephalic (thinking of food) and gastric (eating food) digestion, anticipation of food and food stretching the stomach causes an increase in pancratic secretions. |
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Gastrin and Histamine |
Stimulate Parietal Cells (HCI) |
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Acetylcholine and Histamine |
Act directly on the parietal cells to increase hydrogen and chloride ion production |
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Gastrin |
acts indirectly by causing the ECL cells to release histamine. |
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Cephalic Phase of Secretion |
Begins when an animal anticipates or is preparing to eat a meal. Acetylcholine from nervous system stimulates: 1. Parietal Cells = to secrete HCI into stomach 2. Chief Cells = to secrete pepsinogen into stomach 3. G Cells = to secrete gastrin into bloodstream Then, Gastrin travels to the parietal and ECL cells to stimulate: 1. ECL cells = to release histamine 2. Parietal Cells = to secrete HCI Acetylcholine can also trigger histamine release by ECL cells. Histamine further stimulates the parietal cells to produce more HCI |
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Gastric Phase of Secretion |
Begins when food enters the stomach. Glandular cells are further stimulated by the stomach wall stretching. Formation of peptides by protein breakdown stimulate G cells. In addition, acetylcholine released stimulates the secretion of histamine from the ECL cells and gastrin from the G Cells. Gastrin stimulates more histamine from ECL Cells, which in turn increases HCI production. Peptides have a direct effect on the release of gastrin by G Cells, ultimately leading to more histamine release, to increase HCI production. pH in stomach can be as low as 2.0 |
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Chemical Digestion (Small Intestine) |
Many secretions are released from the small intestine that contribute to the digestive process. The duodenal mucosa secretes 2 important hormones: 1. Cholecystokinin (CCK) 2. Secretin |
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Cholecystokinin Stimulus (CCK) |
The stimulus for secretion of CCK is the presence of chyme with high amino acid concentration, high fatty acid concentration, low pH entering the sm intestine. CCk is the major stimulus for contraction of gallbladder and relaxation of the sphincter of oddi, allowing bile to enter the duodenum. |
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Cholecystokinin Function (CCK) |
The role of CCK: 1. Inhibits gastric emptying - allows chyme to exit tummy at controlled rate, to neutralize the stomach acid to protect small intestines. 2. Increases secretion of pancreatic digestive proenzymes as well as bicarbonate. 3. Triggers for gallbladder to contract, releasing bile. 4. Stimulates secretion of enteropeptidase |
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Enteropeptidase |
Is responsible for converting one of the pancreatic proenzymes (Inactive form), tripsinogen into its active form trypsin. CCK stimulates mucosal cells to secrete enteropeptidase. Enterepeptidase activates tripsinogen into trypsin. Trypsin activates other proenzymes like chymotrypsinogen into chmotrypsin, proelastase into elastase. |
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Secretin |
Hormone released by the duodenal, decreases the HCI production in the stomach, and increases pancreatic and biliary bicarbonate secretion. The stimulus for secretin release is the presence of chyme with a low pH or high fatty acid concentration. Digestive enzymes released from pancrease function best when pH is more alkaline than acidic chyme. The release of bicarbonate from pancreas and liver neutralize the acid leaving the stomach, ensuring pancreatic digestive enzymes are most effective. |
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Insulin |
Needed to transport glucose into most cells, thereby lowering the glucose level in the blood. secreted by beta cells. |
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Pancreatic Enzymes |
Enzymes derived from the exocrine pancreas are vital to the digestion of proteins, carbohydrates, lipids, and nucleic acids. |
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Lipases |
Break down lipids (fats) into 2 free fatty acids and a monoglyceride |
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Amylase |
Breaks down starches into maltose (sugar) Carbohydrates |
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Nucleases |
Breakdown nucleic acids into nucleotides DNA, RNA |
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Proteases |
Breakdown proteins into Amino Acids |
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Proenzymes |
All proteolytic enzymes are secreted by the pancreas in an inactive form called proenzymes. These proenzymes need to be activated in the lumen of the intestine, just like pepsinogen, the proenzyme released by chief cells in the stomach. |
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Metabolic Waste Excretion |
Chemical reactions are of great benefit to the body but also result in the production of many by-products, some can be recycled. Other by-products are of no further use and can be harmful if accumulated. Ex: - Carbon dioxide & water from carbohydrate and fat metabolism - Nitrogenous wastes, primarily urea from protein metabolism - Bile salts and pigments from red blood cell breakdown - various salts from tissue breakdown and excessive consumption |
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Routes for waste Product Elimination |
- Respiratory system removes carbon dioxide and water vapor - Sweat glands eliminate water, salts, and a small amount of urea - Digestive system removes bile salts and bile pigments - Urinary system removes urea, salts, water and other soluble waste products |
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The Urinary System |
The single most important route of waste-product removal in the body. It removes nearly all the soluble waste from blood and transports it out of the body. The urinary system is also a major route for the elimination of excess water from the body. |
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Parts of the Urinary System |
- 2 kidneys that make urine and carry out other vital functions - 2 ureters that carry urine to the urinary bladder - One urinary bladder that collects, stores, and releases urine - One urethra that conducts urine from the body. |
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Kidney Functions |
Most obvious function is the production of urine to facilitate the elimination of metabolic waste materials from the body. In the process of making urine, it also helps maintain homeostasis by manipulating the composition of blood plasma. Kidney regulates body acid and electrolytes balance and filters water out of the blood to equal amount that is being put in. Ex: levels of sodium, potassium, chloride, nitrogenous waste (urea). |
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Kidney Homeostasis |
Kidney regulates: - Blood filtration, reabsorption, and secretion - Fluid Balance Regulation - Acid Balance Regulation - Hormone Production - Blood Pressure Regulation |
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Blood Filtration, Reabsorption, Secretion |
The blood is filtered, useful substances are returned to the circulation, and waste products are secreted from the bloodstream into the fluid that eventually becomes urine. |
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Fluid Balance Regulation |
Amount of urine produced depends on the amount of water it contains, which helps ensure that the body contains the right amount of water to maintain a healthy internal environment. If body has excess water, more urine is formed (diuresis). If body needs to conserve water, less urine is produced (Oliguria) or no urine at all (anuria). Amount of water contained in urine is under the control of the hormone antidiuretic hormone (ADH) and aldosterone. |
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Acid Base Balance Regulation |
Kidneys help maintain acid base balance homeostasis by their ability to remove acidic hydrogen and basic bicarbonate ions from the blood and excrete them in urine. By eliminating ions in the appropriate amounts, blood pH can be maintained in proper range. |
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Hormone Production |
Kidneys have close connection with endocrine system- hormones that help regulate body functions. Ex: the kidney can influence the rate of release of ADH. Specialized cells in the kidneys produce erythropoietin, the hormone necessary for red blood cell production in bone marrow. |
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Blood Pressure Regulation |
Kidneys contain internal receptors that monitor blood pressure. When blood pressure falls, the kidneys secrete a hormone called renin. The release of renin will start a cascade of reactions that will result in vasoconstriction and the retention of sodium by water. Increasing the fluid volume of blood, blood pressure will also be increased. |
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Kidney Location |
Located in the dorsal part of the abdomen, just ventral to and on either side of the first few lumbar vertebrae. In common domestic animals, except the pig, the right kidney is more cranial than the left. A thick layer of fat usually surrounds the kidneys to protect them. The right kidney is less mobile because it fits into a depression of the liver. Left kidney is more mobile. |
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Retroperitoneal |
Kidneys are located retroperitoneal to the abdominal cavity; that is, they are outside the parietal peritoneum and are therefore considered officially outside the abdomen. Kidneys move with movement of the diaphragm. |
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Kidney Gross Anatomy |
Bean shaped and covered by a fibrous connective tissue capsule. The kidney of domestic animals have a smooth surface. The surface of cattle are divided into 12 lobes that give it a lumpy appearance. |
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Hilus |
The indented area on the medial side of the kidney is called the hilus. This is the area where blood and lymph vessels, nerves and the ureters enter and leave the kidney. |
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Renal Pelvis |
A funnel shaped area inside the hilus known as the renal pelvis (center). It is a urine collection chamber that forms the beginning of the ureter. It is lined with transitional epithelium (stretchable). Cattle do not have renal pelvis. |
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Renal Cortex |
The outer portion of the kidney is called the renal cortex. It is a reddish brown nd has glandular appearance. |
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Renal Medulla |
The inner portion around the renal pelvis is the renal medulla. It has a smooth appearance w/ dark purple outer area that sends rays up into the cortex and a pal, gray red inner area that extends down to the renal pelvis. |
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Microscopic Anatomy of Kidneys |
Within the cortex and medulla of kidneys are packed many, many of microscopic filtering, reabsorbing, and secreting units called nephrons. |
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Nephrons |
Is the smallest, basic functional unit of the kidney. Number of nephrons per kidney varies by species. Each nephron is composed of: - Renal Corpuscle - Proximal Convulated tubule (PCT) - Loop of Henle - Distal Convulated Tubule (DCT) |
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Renal Corpuscle |
Located in the cortex of the kidney. It is made up of the glomerulus and bowmans capsule. |
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Glomerulus |
Is a tuft of glomerular capillaries |
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Bowmans capsule |
A double walled capsule that surrounds the glomerulus. Inner layer of browmans capsule is the visceral layer, and it adheres closely to the surface of all glomerular capillaries. The outer layer is called the parietal layer. |
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Podocytes |
The visceral layer of bowmans capsule is made up of podocytes that have footlike extensions that cover the glomerular capillaries. The podocytes covering the capillaries have spaces between them, creating a permeable layer through which fluid and dissolved substances can pass during filtration. |
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Capsular Space |
The space between the visceral and parietal layers is the capsular space. Capsular space is continous with the proximal convulated tubule |
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Glomerular Filtrate |
The function of the renal corpuscle is to filter blood in the first stage of urine production. The fluid that is filtered out of blood is called glomerular filtrate. Circular filtration where water and glucose squeeze out through here. |
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Proximal Convulated Tubule (PCT) |
It is continuous of the capsular space of bowmans capsule. Longest part of the tubular system of the nephron. Epithelial cells that line the PCT are cuboidal and have a brush border for increase surface area. Important for reabsorption and secretion functions. |
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Tubular Filtrate |
The glomerular filtrate, now called the tubular filtrate begins its journey through the tubular part of the nephron in the PCT. |
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Loop of Henle |
Continues from the PCT, descends into the medulla of the kidney, makes a Uturn and heads back up into the cortex. Descending part of loop of henle has cuboidal epithelial cells like PCT. As it makes its u turn, the wall becomes thinner and epithelial cells flatten to simple squamous epithelial. As the loop of henle ascends back up into cortex, its wall become thicker again. |
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Distal Convoluted Tubule (DCT) |
Continuation of ascending part of loop of henle. The DCT follows a twisting path through the cortex. Even though it is called convoluted tubule, it is not as twisted as PCT. |
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Collecting Ducts |
The distal convoluted tubules from all the nephrons in the kidney empty into a series of tubules called collecting ducts. They carry the tubular filtrate through the medulla into the calyces, which lead to the renal pelvis. The collecting ducts also play an important role in urine volume because they are the primary site of action of antidiuretic hormone (ADH). Potassium regulation and acid base balance control are 2 functions that take place here as well. |
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Blood Supply to kidneys |
Very large blood supply in the kidneys, which makes sense because its job is to clear waste products from the blood. up to 25% of blood pumped by heart goes to kidneys. it circulates every 4 or 5 mins. Main blood vessels have unique functions. - Renal Artery - Afferent Glomerular Arterioles - Glomerular Capillaries - Efferent Glomerular Arterioles - Peritubular capillaries -Renal Vein |
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The Renal Artery |
It branches off the abdominal portion of the aorta. It enters kidneys at the hilus. It then divides and subdivides into smaller arteries and arterioles until it becomes a series of afferent glomerular arterioles. |
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Afferent Glomerular Arterioles |
They carry blood into the glomerular capillaries of the renal corpuscle. (blood coming into the circle filter) |
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The glomerular Capillaries |
They are a continuation of the afferent arterioles. They filter some of the plasma out of the blood, which enters the capsular space of bowmans capsule, where it is known as the glomerular filtrate. The blood in the glomerular capillaries leaves the glomerulus and enters the efferent glomerular arterioles. No oxygen has been exchanged yet. |
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Efferent Glomerular Arterioles |
It divides into a network of capillaries that surrounds the rest of the nephron. These capillaries are known as the peritubular capillaries. Oxygen transfer to the cells of the nephron takes place here. Also, substances are taken out of the tubular filtrate and put back into blood. (Tubular Reabsorption) Other substances are secreted from blood into tubules (tubular secretion). |
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Peritubular capillaries |
They surround the nephron and converge to form venules that in turn converge to form larger veins that eventually become the renal vein. |
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Renal Vein |
Leaves the kidneys at the hilus and joins the abdominal portion of the caudal vena cava. The blood in the renal veins is the purest blood in the body. |
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Filtration of Blood |
Filtration of blood occurs in the renal corpuscle. Glomerular capillaries are found between two arterioles and have a high blood pressure. High blood pressure is created by diff. size in afferent and efferent glomerular arterioles. Efferent arterioles are smaller causing blood to build up within glomerular capillaries. High blood pressure in glomerular capillaries forces some plasma out into capsular space of bowmans capsule. |
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Fenestrations |
The transfer of plasma out of the glomerular capillaries is helped by the presence of many fenestrations, or pores in the capillary endothelium. These fenestrations are larger than the fenestrations found in the endothelium of other capillaries, and they allow more fluid to leave the bloodstream. |
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Glomerular Filtrate |
This fluid is known as the glomerular filtrate when it enters the capsular space and is similar to plasma except that it contains virtually no proteins. |
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Glomerular Filtration Rate |
Term used to describe how fast plasma is filtered as it passes through the glomerulus. GFR depends on the rate of blood flow to the kidney. |
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Reabsorption |
Once plasma leaves the circulation and passes into the capsular space to become the glomerular filtrate, it is considered to be outside the body. Glomerular filtrate is composed of fluid containing small molecules that fit through the glomerular fenestration. These are waste products that can get reabsorbed. They leave tubules from the nephrons and enterblood of the peritubular capillaries to maintain homeostasis such as: - water - glucose - amino acids - ions - bicarbonate - calcium - magnesium |
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Secretion |
Many waste products are not filtered from the blood in the glomerular capillaries. The body needs to get rid of them so it transfers them from the peritubular capillaries to the interstitial fluid to the tubular epithelial cells and into the tubular filtrate in the tubules. Most secretion takes place in the DCT. Ex: hydrogen, potassium, ammonia are secreted. Some medication also is eliminatedd by secretion. |
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Urine Volume Regulation |
Urine volume is determined by the amount of water contained in the tubular filtrate (waste) when it reaches the renal pelvis. It is controlled by the actions of 2 hormones: 1. Antidiuretic hormone (ADH) released from posterior pituitary gland 2. Aldosterone secreted by the adrenal cortex. |
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Antidiuretic Hormone (ADH) Urine Volume |
ADH plays the most important role in regulating urine volume. If ADH is absent, water will not be reabsorbed and will be lost making more urine (Polyuria). If ADH is present more water will be reabsorbed and will make less urine. |
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Aldosterone |
It increases reabsorption of sodium into the bloodstream in the DCT and collecting ducts. It causes water to follow sodium out of the tubular filtrate and into the blood. |
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Regulation of Blood Pressure |
Kidneys help maintain homeostasis by playing an important role in regulating blood pressure. When blood pressure falls a system called renin - angiotensin - aldosterone system responds to bring it back up to a normal level. |
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Renin - Angiotensin - Aldosterone system |
Justaglomerular cells will respond by releasing renin. Renin causes aldosterone to be released from the adrenal glands. By releasing aldosterone, it increases sodium and water reabsorption back to the bloodstream, aldosterone will cause an inrease in blood volume. As blood volume increases, it will better fill the vascular space and increase blood pressure. |
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Ureters |
The ureter is a tube that exits the kidney at the hilus and connects to the urinary bladder near the neck of the bladder at its caudal end. The two openings from the ureters into the bladder and the opening from the bladder into the urthra, this arrangement is reffered to as the trigone of the bladder. It is a continuation of the renal pelvis. |
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Ureters Anatomy |
Ureters are tubes composed of 3 layers: - Fibrous Layer (Outer) - Muscular Layer (Middle) - Smooth Muscle - Epithelial layer (Inner) - Transitional Epithelial The ureters are a continuation of the renal pelvis and each ureter leaves its kidney at the hilus |
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Ureter Function |
Smooth muscle layers propels the urine through the ureter by peristaltic contractions, like intestinal contraction. The ureters enter the urinary bladder at such an oblique angle that when the bladders is full, it collapses the opening of the ureter, preventing urine from backing up into the ureter. It still allows urine to enter the bladder, but not from backing up into the ureters. |
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Urinary Bladder |
It stores urine as it is produced and releases it periodically. It has 2 parts: 1. Muscular Sac 2. Neck |
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Anatomy of Urinary Bladder |
The size and position of bladder depend on the amount of urine it contains. Bladder is lined with transitional epithelium that stretches the bladder as it fills with urine. |
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Detrusor Muscle |
Urinary bladder contains smooth muscle called detrusor muscle. When these muscles contract, the bladder is squeezed and urine is expelled. Around the neck of the urinary bladder are circular sphincter muscles composed of skeletal muscle fibers. These muscles are under voluntary control to open and close passageway for urine to leave the bladder. |
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Function of Urinary Bladder |
It collects, stores, and releases urine. Kidneys constantly produce urine, so if it weren't for the storage function of the urinary bladder, animals would constantly drip urine as it was being produced |
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Urethra |
Is a continuation of the neck of the urinary bladder that runs through the pelvic canal. It is lined with transitional epithelium to allow it to expand. |
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Urethra Function |
It carries urine from the urinary bladder to the external environment. |
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Female Urethra |
It is shorter and straighter than the long, curved male urethra. Urethra opens on the floor (ventral portion) of the vestibule of the vulva. It is lined with transitional epithelium. In the female, the urethra has a strictly urinary function; it carries only urine |
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Male Urethra |
The urethra runs along the ventral aspect of the penis. In males, the urethra also has a reproductive function + urinary function. The urethra carries urine or semen. At the beginning of ejaculation, the sphincter at the neck of the urinary bladders closes to prevent semen from entering the bladder and mixing with urine. |
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Urination aka Micturition aka Uresis |
Is the expulsion of urnie from the urinary bladder into the urethra for elimination from the body. The process involves 2 to 3 steps: - Urine Accumulation - Muscle Contraction - Sphincter Muscle Control |
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Urine Accumulation |
The urinary bladder constantly accumulates urine, until the pressure of the filling bladder reaches a certain trigger point that activates stretch receptors in the bladder wall. |
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Muscle Contraction |
When the trigger point is reached, a spinal reflex is activated that returns a motor impulse to the detrusor muscle and the smooth muscle of the bladder wall contracts. These contractions are responsible for the sensation of having to urinate. |
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Sphincter Muscle Control |
Animals that have been trained can control the reflex release of urine by voluntary control of the muscular sphincter around the neck of the bladder. This results in temporary control of urination. The fuller the bladder gets, the more pressure is applied to the muscular sphincter, until it eventually relaxes, and urine is released. |
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Mass Movement Poop |
Consists of a period of intense propulsive activity, moving the contents of the Lg intestine toward the rectum. Mass movement contractions occur within both the colon and the cecum. |
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Female Reproductive System |
The female reproductive system is a bit more complex than the male part because it has more jobs to do: - Production of sex hormones and development of gametes - The female system receives the gametes - Provides a hospitable environment for the embryo to grow and develop - Pushes the offspring out into the world when it is fully developed. - furnishes a site for them to fertilize the ovum |
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Ovaries |
They ovaries are the females gonads; they are the female equivalent of the males testes. |
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Ovaries Characteristics |
They are located in the dorsal part of the abdominal cavity near the kidneys. Their shape varies among species; in most, they are somewhat almond shaped, but the ovaries in the horse are indented, bean liked shaped. Caudal to kidneys |
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Ovaries Functions |
2 main functions: 1. Producing gametes in follicles 2. Producing hormones |
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Oogenesis |
Is the process by which ova (female gametes) are produced in follicles in the ovaries. Unlike spermatozoa, ova are not constantly produced during the reproductive life of the animal. |
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Oocytes |
At or soon after birth, ovaries are seeded with tens of thousands of immature reproductive cells called oocytes. Some of these oocytes will mature into ova, the mature female reproductive cells, through the activities of the ovarian cycle. The rest will either degenerate or never begin development. |
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Reproductive hormones |
The hormones produced in the ovaries fall into two categories: - Estrogen - Progestin |
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Estrogen |
are produced by the cells of the developing ovarian follicles and are responsible for the physical and behavioral changes that prepare the animal fro breeding and pregnancy |
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Progestin |
principally progesterone, are produced by the corpus luteum that develops from the empty follicle after ovulation. Progestins help prepare the uterus for implantation of a fertilized ovum. They are also necessary for pregnancy to be maintained once implantation occurs. |
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Ovarian Cycle |
Ova are not constantly produced in the ovaries. Their production involves a complex sequence of events carried out in a cyclic (repeating) fashion under the influence of 2 hormones: 1. Follicle Stimulating Hormone (FSH) 2. Luteinizing Hormone (LH) |
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Uniparous |
The number of follicles involved in each cycle depends on the species. Uniparous species, such as horses, cattle, and humans normally give birth to only 1 offspring at a time. The ovaries produce one mature ovum per cycle. |
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Multiparous |
Species such as cats, dogs, and sows give brith to litters of young. Their ovaries produced multiple ova per cycle. |
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Primary Follicle |
The beginning stage of follicle development in the ovary is the primoridal, sometimes called the primary follicle. The thousands of immature oocytes in the ovaries of newborn animals reside in this stage until they become activated later in life and begin to develop further. |
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Growing Follicle |
Once a primordial follicle has become activated, it is referred to as a growing follicle. The oocyte starts to grow in size, the glycoprotein zona pellucida layer forms just outside the cell membrane, and the follicular cells enlarge into cuboidal shapes and begin to multiply. |
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Mature Follicle |
When the follicle has reached its maximum size, it looks like a large, blisterlike structure on the surface of the ovary. |
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Ovulation |
Rupture of the mature follicle with release of the reproductive cell into the oviduct. At this stage, estrogen production from the follicle is at a peak level, and the animal is ready for breeding to take place. |
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Ovum |
Once the mature gamete is released from the follicle, it is now called the ovum. |
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Corpus Luteum |
Produces the hormone progestin needed to maintain pregnancy if ovum is fertilized. If the ovum has been fertilized and implants in the uterus, it sends an endocrine signal to the ovary that causes the corpus luteum to be maintained. If the ovum has not been fertilized, no "we are pregnant" endocrine signal is sent and the corpus luteum degenerates after a short period. |
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Follicular Artresia |
Not all follicles that were activated in a particular ovarian cycle fully develop and ovulate. It is as if the ovary "auditions" follicles and chooses particular ones to fully develop. The rest may degenerate at any stage of their development. This is called follicular atresia and is a normal part of each ovarian cycle. |
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Oviducts |
2 oviducts also are known as the fallopian tubes and uterine tubes, small convoluted tubes that extend from the tips of the uterine horns. Their roles are to guide ova from the ovary to the uterus and to serve as the usual site for fertilization of ova by spermatozoa. |
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Infundibulum |
The oviducts are not attached to the ovaries at all; when ovulation takes place, they have to catch the ova in the funnel like infundibulum, which is the enlarged opening at the ovarian end of each oviduct. |
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Fimbriae |
Muscular, fingerlike projections called fimbriae form the margin of the infundibulum. They feel along the surface of the ovary and position the infundibulum where the follicles are located. This helps ensure that the infundibulum is properly positioned to catch the ova when ovulation occurs. |
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Uterus |
Is the womb, where the fertilized ovum implants and lives while it grows and develops into a new animal. It is a hollow muscular organ. In domestic animals, it is somewhat Y shaped, with the uterine body forming the base of the Y and the two uterine horns forming the arms. |
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Placenta |
The uterus forms part of the placenta, which is the life support system that keeps the fetus alive while it develops during pregnancy. |
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Afterbirth |
After it has delivered the newborn and the placenta, it has to contract quickly to stop bleeding from the sites where the placenta was attached to its lining. |
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Uterus Layers |
It has 3 layers: 1. endometrium - composed of simple columnar epithelium and simple tubular glands that secrete mucus 2. myometrium- the thickest layer of the wall made of smooth muscle to help push the fetus 3. perimetrium - the outer most layer covered by the visceral layer of peritoneum |
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Cervix |
Is a muscular valve that seals off the uterus from the outside most of the time. It functions to control access to the lumen of the uterus from the vagina. The cervix is normally tightly closed, except at the two ends of pregnancy: estrus (heat period) and parturition (birth process) |
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Estrus |
It relaxes at estrus to admit spermatozoa during breeding. It then tightly closes again during pregnancy and does not relax again until birthing time. |
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Vagina |
Is the tube that receives the penis at breeding time and acts as the birth canal at parturition. It is a muscular tube that extends audally from the cervix and connects it with the vulva. |
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Vulva |
Its main parts are the vestibule, clitoris, and labia. Urethra opens on the floor of the vestibule. The only portion of the female reproductive system that is visible from the outside. |
