Pointers for the Final Examination in MB105 PDF

Pointers for the Final Examination in MB105 Chapter 17: Blood Blood consists of plasma and formed elements, which are cells or cell fragments. When analyzing a blood smear, the main focus is on the formed elements: red blood cells, platelets, and white blood cells....

Pointers for the Final Examination in MB105 Chapter 17: Blood Blood consists of plasma and formed elements, which are cells or cell fragments. When analyzing a blood smear, the main focus is on the formed elements: red blood cells, platelets, and white blood cells. Red blood cells (RBCs), also known as erythrocytes, are the most common formed element in blood, with approximately 5 million per microliter. They are biconcave disks with a pale central region due to their shape. RBCs circulate for approximately 120 days before being destroyed and their components recycled. A complete blood count (CBC) is a common blood test. The CBC determines the number of red blood cells, platelets, and white blood cells. It also measures other parameters such as hemoglobin. White blood cells (WBCs), also known as leukocytes, are an important part of the immune system and help fight infection. There are different types of WBCs, each with unique functions. A CBC provides the total number of WBCs and can also determine the numbers of each type. Platelets are small cell fragments involved in blood clotting. Plasma cells are a type of white blood cell that develops from B lymphocytes. Plasma cells are responsible for producing antibodies, which are proteins that help fight infection. They are characterized by a cytoplasm filled with rough endoplasmic reticulum (RER), which is needed for antibody production. Plasma cells also have a large amount of heterochromatin, reflecting the fact that they produce large numbers of copies of just a few proteins (antibodies). Monocytes are large white blood cells that can differentiate into macrophages, which are phagocytic cells that engulf and destroy foreign substances and cellular debris. Monocytes have a kidney bean-shaped nucleus. Lymphocytes are another type of white blood cell and are involved in both the innate and adaptive immune responses. Lymphocytes are smaller than monocytes. Eosinophils are a type of white blood cell involved in allergic reactions and fighting parasites. They have a bilobed nucleus and prominent eosinophilic granules in their cytoplasm. Basophils are a type of white blood cell that releases histamine and other mediators involved in inflammatory responses. They have a segmented nucleus that is often obscured by the many large, basophilic granules in their cytoplasm. Chapter 18: Hematopoiesis Overview Hematopoiesis is the process of blood cell production. It occurs in the bone marrow after birth. Before birth, hematopoiesis takes place in other locations like the yolk sac, liver, and spleen. In certain diseases, hematopoiesis may also occur in these organs after birth. Jefferson E. Flores, MAEd, RN, LPT Assistant Professor Medical biology  Pointers for the Final Examination in MB105 This chapter focuses on the major cellular features used to distinguish developing blood cell types. These features include: o Cytoplasmic granules: presence, type, and size o Presence or absence of nucleoli o Shape of the nucleus: round, indented, kidney bean-shaped, band, segmented o Extent of nuclear chromatin clumping: fine or clumped o Degree of cytoplasmic basophilia or eosinophilia Identifying these features helps distinguish the developmental stages in blood cell maturation. Chapter 19: Hematopoiesis: White Blood Cells and Platelets All blood cells originate from a common hematopoietic stem cell. This stem cell gives rise to different progenitor cells that commit to specific cell lineages, such as the lymphoid or myeloid lineages. Myeloblasts are the earliest recognizable precursors in the granulocyte lineage. They are large cells with basophilic cytoplasm, a fine chromatin pattern, and prominent nucleoli. Promyelocytes share similarities with myeloblasts but have primary (azurophilic) granules. They are larger than myeloblasts. It is difficult to determine from a routine blood smear if a myeloblast or promyelocyte will develop into a neutrophil, eosinophil, or basophil. A "left shift" is an increase in the number of immature white blood cells, particularly band cells, in the peripheral blood. This often indicates an ongoing infection, commonly a bacterial infection. Megakaryocytes are the cells responsible for producing platelets. They are large cells with a multilobed nucleus and abundant cytoplasm. They reside in the bone marrow adjacent to sinuses, which are capillaries within the marrow. Megakaryocytes release fragments of their cytoplasm and plasma membrane into the bloodstream, forming platelets. Chapter 20: Hematopoiesis: Red Blood Cells A key difference between erythrocyte and granulocyte development is that RBCs lack cytoplasmic granules. As red blood cells mature, they produce increasing amounts of hemoglobin, the protein responsible for oxygen transport. This leads to a change in their staining characteristics, becoming less basophilic and more eosinophilic as they mature. Jefferson E. Flores, MAEd, RN, LPT Assistant Professor Medical biology  Pointers for the Final Examination in MB105 Reticulocytes are immature red blood cells that still contain some RNA. They are slightly larger than mature RBCs. They are released from the bone marrow into the bloodstream and mature into erythrocytes within a few days. Chapter 28: Overview of the Gastrointestinal System The gastrointestinal (GI) system is a continuous tube responsible for the breakdown and absorption of ingested nutrients. The wall of the GI tract is generally organized into four distinct layers. Mucosa: The innermost layer is the mucosa. It is composed of three sublayers: o Epithelium: The type of epithelium varies depending on the specific location within the GI tract. o Lamina propria: The lamina propria is a layer of loose connective tissue that contains blood vessels, nerves, lymphatics, and glands. o Muscularis mucosae: The muscularis mucosae is a thin layer of smooth muscle. Submucosa: The submucosa is a layer of dense irregular connective tissue. It contains larger blood vessels, nerves, lymphatics, and glands. Muscularis externa: The muscularis externa is responsible for the motility of the GI tract. It has two smooth muscle layers: o Inner circular layer o Outer longitudinal layer Serosa/Adventitia: The outermost layer is either a serosa, if covered by mesothelial cells, or an adventitia, if it directly blends with surrounding tissues. The mucosa of the small intestine has specialized features to increase surface area for absorption. These features include: o Plicae circulares (valves of Kerckring): These are circular folds of the mucosa and submucosa that are visible to the naked eye. They are permanent folds and help slow the passage of food, increasing the time for digestion and absorption. o Villi: Villi are finger-like projections of the mucosa that are visible with a light microscope. They are covered by epithelial cells and contain a core of lamina propria. o Microvilli: Microvilli are microscopic projections of the plasma membrane of the epithelial cells lining the villi. They form the brush border and further increase the surface area for absorption. Jefferson E. Flores, MAEd, RN, LPT Assistant Professor Medical biology  Pointers for the Final Examination in MB105 The enteric nervous system is a network of nerves within the wall of the GI tract that controls many of its functions, including motility and secretion. It includes two main plexuses: o Myenteric plexus (Au Auerbach's plexus): Located between the circular and longitudinal muscle layers of the muscularis externa. o Submucosal plexus (Meissner's plexus): Found within the submucosa. Enteroendocrine cells are specialized cells scattered throughout the epithelium of the GI tract. They release hormones basally into the lamina propria, which can act locally or enter the bloodstream to affect distant organs. Chapter 29: Intestines The intestines are responsible for the final stages of digestion and absorption of nutrients. The small intestine is the primary site for the chemical breakdown of organic molecules and the absorption of nutrients. It is divided into three regions: o Duodenum: The duodenum receives chyme from the stomach, as well as bile from the liver and pancreatic secretions. It has unique histological features, including:  Brunner's glands (submucosal glands): These glands secrete an alkaline mucus that helps neutralize the acidic chyme entering from the stomach.  Ampulla of Vater: This is the point where the common bile duct and the pancreatic duct join and enter the duodenum. o Jejunum: The jejunum is characterized by having all the main features of the small intestine, including plicae circulares, villi, microvilli, intestinal crypts, and numerous Paneth cells. It is the most active site for nutrient absorption in the small intestine. o Ileum: The ileum is similar to the jejunum in its overall structure. However, it contains Peyer's patches, which are large lymphoid nodules located on the antimesenteric side of the ileum. These patches play a role in immune surveillance of the gut. The epithelium of the small intestine is composed of several cell types: o Enterocytes (intestinal absorptive cells): Enterocytes are the most numerous cell type in the small intestine epithelium. They have elaborate microvilli that form the brush border. Enterocytes express digestive enzymes on their brush border and are responsible for absorbing nutrients. They have basally located nuclei and eosinophilic cytoplasm. o Goblet cells: Goblet cells are interspersed among the enterocytes and are easily recognized in H&E-stained sections because their mucus-containing secretory granules do not stain well, giving them a pale or clear appearance. They secrete mucus that lubricates and protects the intestinal lining. Jefferson E. Flores, MAEd, RN, LPT Assistant Professor Medical biology  Pointers for the Final Examination in MB105 o Stem cells: Stem cells are located in the intestinal crypts and are responsible for replacing cells lost during normal epithelial turnover. They are not easily identifiable in routine H&E-stained sections. o Enteroendocrine cells: These cells release hormones that regulate various digestive processes. They are scattered throughout the epithelium and are not visible in routine H&E-stained sections. o Paneth cells: Paneth cells are located at the base of the intestinal crypts. They produce antibacterial proteins, such as lysozymes and alpha-defensins, which help protect the intestine from harmful bacteria. Their secretory granules are large and eosinophilic. The large intestine primarily functions to absorb water and convert fecal material from liquid to solid. It has some histological similarities to the small intestine but also has distinct features: o Lacks villi: The large intestine does not have villi, resulting in a smoother luminal surface compared to the small intestine. o Few Paneth cells: Paneth cells are typically scarce or absent in the large intestine. o Abundant goblet cells: The large intestine has a higher proportion of goblet cells compared to the small intestine, contributing to the production of more mucus for lubrication and protection. Chapter 30: Oral Cavity, Tongue, and Salivary Glands The tongue is a muscular organ in the oral cavity. It is covered by stratified squamous epithelium and has a core of skeletal muscle. The dorsal surface of the tongue has projections called papillae, which can be classified into four types: o Filiform papillae: Filiform papillae are the most numerous type of papillae. They are conical in shape and are keratinized, giving the tongue a rough texture. They do not contain taste buds. o Fungiform papillae: Fungiform papillae are mushroom-shaped and are scattered among the filiform papillae. They are less keratinized than filiform papillae and may contain taste buds on their upper surface. o Foliate papillae: Foliate papillae are leaf-shaped and are found on the lateral edges of the tongue. They are not well-developed in humans. o Circumvallate papillae: Circumvallate papillae are the largest type of papillae and are arranged in a V-shape at the back of the tongue. They are surrounded by a deep groove or moat. Circumvallate papillae are rich in taste buds, which are located along the sides of the papillae. They also have serous glands (Von Ebner's glands) that secrete a watery fluid into the moat, helping to wash away food particles and allow for continuous taste perception. Jefferson E. Flores, MAEd, RN, LPT Assistant Professor Medical biology  Pointers for the Final Examination in MB105 Taste buds are sensory organs that detect different tastes. They are located in the epithelium of the tongue, particularly in the circumvallate and fungiform papillae. There are three pairs of major salivary glands, which are exocrine glands that secrete saliva into the oral cavity: o Parotid gland: The parotid gland is the largest of the salivary glands. It is located in front of and below the ear. The parotid gland has a distinctive histological feature: it contains only serous acini, meaning it produces a watery, enzyme-rich saliva. o Submandibular gland: The submandibular gland is located beneath the mandible (lower jaw). It produces a mixed secretion, containing mostly serous acini with some mucous acini. Mucous acini produce a more viscous, mucus-rich saliva. o Sublingual gland: The sublingual gland is the smallest of the major salivary glands and is located under the tongue. It produces a predominantly mucous secretion, with mostly mucous acini and a few serous acini. Salivary glands are organized into lobes and lobules. Each lobule contains a common duct that drains the secretions from the secretory units within that lobule. Ducts from adjacent lobules combine to form larger ducts, which eventually drain the entire gland. The secretory units of salivary glands are called acini, which are clusters of secretory cells. Acini can be either serous or mucous, depending on the type of secretion they produce. Some acini have a mixture of serous and mucous cells. Serous demilunes are clusters of serous cells found at the edge of mucous acini. Salivary gland ducts modify the initial saliva secreted by the acini. They can be classified into three types: o Intercalated ducts: Intercalated ducts are the smallest ducts and are located closest to the acini. They are lined by a simple cuboidal epithelium and have minimal activity in modifying saliva. o Striated ducts: Striated ducts are larger than intercalated ducts and are lined by a simple columnar epithelium. The epithelial cells of striated ducts have elaborate basolateral infoldings of the plasma membrane, giving them a striated appearance in light microscopy. These infoldings increase the surface area for ion transport. Striated ducts are actively involved in modifying the ionic composition of saliva, making it hypotonic. o Excretory ducts: Excretory ducts are the largest ducts and function to transport saliva to the oral cavity. They are lined by a variety of epithelia, from simple columnar to stratified squamous, depending on their size and location. Chapter 31: Pharynx, Esophagus, and Stomach Jefferson E. Flores, MAEd, RN, LPT Assistant Professor Medical biology  Pointers for the Final Examination in MB105 The pharynx and esophagus are muscular tubes that transport food from the oral cavity to the stomach. The esophagus has a stratified squamous epithelium that protects it from abrasion by swallowed food. The muscularis of the esophagus is unique in that it transitions from skeletal muscle in the upper portion to smooth muscle in the lower portion. This allows for both voluntary and involuntary control of swallowing. The stomach has several functions, including: o Storage of food: The stomach can expand to accommodate large meals. o Production of pepsin and hydrochloric acid: These substances help break down proteins in food. o Mechanical mixing of food: The muscular wall of the stomach churns and mixes food with gastric juices. The stomach is divided into four major regions: o Cardia: The cardia is the region where the esophagus joins the stomach. o Fundus: The fundus is the dome-shaped upper region of the stomach. o Body: The body is the main central region of the stomach. o Pylorus: The pylorus is the lower region of the stomach that connects to the duodenum. Histologically, the stomach can be divided into three regions: o Cardia o Fundus and body o Pylorus The mucosa of the stomach has a unique structure to increase surface area for secretion. Instead of villi, the epithelium of the stomach undulates to form gastric pits, which are deep invaginations. At the base of each pit, two or more gastric glands extend into the lamina propria. The cardia and pylorus regions of the stomach are similar histologically. The epithelium of the surface, pits, and glands in these regions primarily consists of mucous-secreting cells. These cells produce mucus that protects the stomach lining from the acidic environment. The fundus and body regions of the stomach are specialized for the production of digestive secretions. In addition to surface mucous cells and mucous neck cells, the glands in these regions contain two main cell types: Jefferson E. Flores, MAEd, RN, LPT Assistant Professor Medical biology  Pointers for the Final Examination in MB105 o Chief cells: Chief cells are located in the basal portion of the gastric glands. They secrete pepsinogen, an inactive precursor of the enzyme pepsin. Pepsinogen is activated by hydrochloric acid in the lumen of the stomach to form pepsin, which breaks down proteins. Chief cells have abundant rough endoplasmic reticulum (RER) in their basal cytoplasm, reflecting their role in protein synthesis. o Parietal cells: Parietal cells are larger than chief cells and are more numerous in the upper portion of the gastric glands. They have a distinctive appearance with a central nucleus and eosinophilic cytoplasm. Parietal cells are responsible for secreting hydrochloric acid and intrinsic factor. Hydrochloric acid activates pepsinogen and helps create the acidic environment necessary for digestion in the stomach. Intrinsic factor is necessary for the absorption of vitamin B12 in the small intestine. Parietal cells have a unique intracellular structure called intracellular canaliculi that are lined by microvilli and are involved in the secretion of hydrochloric acid. They also contain numerous mitochondria to provide energy for the active transport of ions. Chapter 32: Pancreas The pancreas is an organ located behind the stomach. It has both exocrine and endocrine functions, both of which are essential for digestion and glucose regulation. The exocrine pancreas is the majority of the pancreas. It is made up of serous acini that produce and secrete digestive enzymes into the duodenum. These enzymes help break down carbohydrates, proteins, and fats. The endocrine pancreas makes up only a small portion of the pancreas. It consists of clusters of cells called pancreatic islets (islets of Langerhans) that are scattered throughout the exocrine tissue. The islets secrete hormones, primarily insulin and glucagon, directly into the bloodstream. These hormones regulate blood glucose levels. Acinar cells, the secretory cells of the exocrine pancreas, have a characteristic polarized appearance. They have abundant RER in their basal cytoplasm, reflecting their active role in protein synthesis. They also have numerous secretory granules concentrated in their apical cytoplasm, containing the digestive enzymes they produce. The duct system of the exocrine pancreas is similar to that of salivary glands but lacks striated ducts. Centroacinar cells are unique to the pancreas and are located within the acini. They are the initial duct cells and form the beginning of the intercalated ducts. Centroacinar cells secrete a bicarbonate-rich fluid that helps neutralize the acidic chyme entering the duodenum from the stomach. Intercalated ducts are lined by a low cuboidal epithelium and receive secretions from the acini, including the bicarbonate-rich fluid from centroacinar cells. Jefferson E. Flores, MAEd, RN, LPT Assistant Professor Medical biology  Pointers for the Final Examination in MB105 Excretory ducts are larger than intercalated ducts and are lined by a simple columnar epithelium. They transport pancreatic secretions into the main pancreatic duct. The pancreatic duct and bile duct join to form the ampulla of Vater, which enters the duodenum. This allows for the coordinated release of pancreatic enzymes and bile into the small intestine for digestion. Chapter 33: Liver and Gallbladder The liver is the largest internal organ and is located in the upper right quadrant of the abdomen. It has a wide range of metabolic functions, including: o Storage of organic molecules: The liver stores glucose as glycogen, and it also stores vitamins and minerals. o Production of plasma proteins: The liver synthesizes most of the plasma proteins, including albumin, clotting factors, and many others. o Degradation of toxins: The liver detoxifies harmful substances, such as drugs and alcohol. o Production of bile: Bile is a fluid that aids in the digestion of fats. It is produced by hepatocytes and secreted into a system of ducts that eventually drain into the duodenum. The liver receives a dual blood supply, meaning it receives blood from two sources: o Hepatic artery: The hepatic artery supplies the liver with oxygenated blood from the systemic circulation. o Hepatic portal vein: The hepatic portal vein carries nutrient-rich blood from the intestines to the liver. This allows the liver to process and store nutrients absorbed from the digestive tract. Blood from both the hepatic artery and hepatic portal vein flows through specialized capillaries in the liver called sinusoids. Sinusoids are discontinuous capillaries, meaning they have gaps between the endothelial cells that line them. This allows for the free exchange of substances between the blood and the hepatocytes. Sinusoids drain into hepatic veins, which eventually empty into the inferior vena cava. Hepatocytes are the main functional cells of the liver. They are large, polygonal cells with abundant cytoplasm. Hepatocytes are both exocrine and endocrine in function. Their exocrine function is the production of bile, while their endocrine function involves the secretion of various substances into the bloodstream. Hepatocytes have an extensive rough endoplasmic reticulum (RER), reflecting their role in protein synthesis. They also have a well-developed smooth endoplasmic reticulum (SER), which Jefferson E. Flores, MAEd, RN, LPT Assistant Professor Medical biology  Pointers for the Final Examination in MB105 is involved in the detoxification of harmful substances and the metabolism of glycogen. Hepatocytes store glycogen, the storage form of glucose, in their cytoplasm. Bile canaliculi are small channels formed by the plasma membranes of adjacent hepatocytes. They are the initial portion of the bile duct system and are too small to be seen with a light microscope. Bile produced by hepatocytes is secreted into the canaliculi. Bile ductules are small ducts lined by a simple cuboidal epithelium that collect bile from the bile canaliculi. They transport bile to larger intrahepatic bile ducts, which are located in the portal triads. The portal triad is a distinctive feature of liver histology. It is a region at the periphery of the classic liver lobule, typically found at the corners of the hexagonal lobule. Each portal triad contains three key structures: o Branch of the hepatic artery: This supplies the liver lobule with oxygenated blood. o Branch of the hepatic portal vein: This carries nutrient-rich blood to the lobule. o Bile duct: This drains bile from the lobule. The classic liver lobule is the structural unit of the liver. It is a hexagonal-shaped structure with a central vein in the center and portal triads at the periphery. Hepatocytes are arranged in plates that radiate from the central vein toward the portal triads. Liver sinusoids are located between the plates of hepatocytes. They are lined by fenestrated endothelial cells and have a discontinuous basal lamina. This allows for the easy passage of substances between the blood and the hepatocytes. The space of Disse (perisinusoidal space) is a narrow space between the sinusoids and the hepatocytes. It contains microvilli that extend from the hepatocytes, increasing the surface area for exchange. The space of Disse also contains hepatic stellate cells (Ito cells), which store vitamin A and play a role in liver fibrosis. Kupffer cells are resident macrophages found in the lining of liver sinusoids. They are part of the mononuclear phagocyte system and are responsible for removing cellular debris, bacteria, and other foreign substances from the blood. The portal liver lobule is a triangular-shaped structure defined by the drainage of bile into a single bile duct. Its center is a portal triad, and its corners are defined by the central veins of three adjacent classic liver lobules. The liver acinus is the functional unit of the liver, representing the smallest unit of liver parenchyma that receives a blood supply. It is an oval-shaped region that includes portions of two adjacent classic liver lobules and is centered on a terminal branch of the hepatic artery and portal vein. Jefferson E. Flores, MAEd, RN, LPT Assistant Professor Medical biology  Pointers for the Final Examination in MB105 Central veins collect blood from the sinusoids within a classic liver lobule. They are small veins with a thin wall. Central veins drain into sublobular veins, which then empty into hepatic veins. Hepatic veins carry blood from the liver to the inferior vena cava. The gallbladder is a pear-shaped sac located under the liver. It stores and concentrates bile produced by the liver. Bile is transported to the gallbladder from the liver via the cystic duct. The gallbladder releases bile into the duodenum through the common bile duct in response to hormonal signals triggered by the presence of fat in the duodenum. The wall of the gallbladder has three layers: o Mucosa: The mucosa is the innermost layer and is lined by a simple columnar epithelium that is specialized for the absorption of water from bile, concentrating it. o Muscularis: The muscularis is a layer of smooth muscle that contracts to expel bile from the gallbladder. o Adventitia/Serosa: The outermost layer is either an adventitia, where the gallbladder is attached to the liver, or a serosa, where it is not. Chapter 34: Kidney Overview The kidneys are paired, bean-shaped organs located in the retroperitoneum. They are responsible for maintaining the homeostasis of body fluids by: o Filtering blood: The kidneys remove waste products and excess water from the blood. o Regulating electrolyte balance: The kidneys control the levels of electrolytes, such as sodium, potassium, and calcium, in the blood. o Maintaining acid-base balance: The kidneys help regulate the pH of the blood. o Producing hormones: The kidneys produce hormones, such as erythropoietin, which stimulates red blood cell production, and renin, which regulates blood pressure. Each kidney is surrounded by a fibrous capsule and can be divided into three main regions: o Cortex: The cortex is the outer layer of the kidney and contains the renal corpuscles and convoluted tubules of the nephrons. o Medulla: The medulla is the inner layer of the kidney. It is organized into renal pyramids, which are cone-shaped structures that contain the loops of Henle and collecting ducts of the nephrons. o Sinus: The sinus is a cavity within the kidney that contains the renal pelvis, calyces, blood vessels, and adipose tissue. Urine produced in the nephrons drains into a system of collecting structures within the kidney. Jefferson E. Flores, MAEd, RN, LPT Assistant Professor Medical biology  Pointers for the Final Examination in MB105 o Renal papilla: The renal papilla is the tip of the renal pyramid, where urine drains into a minor calyx. o Minor calyx: Minor calyces are cup-shaped structures that surround the renal papillae. o Major calyx: Two or more minor calyces join to form a major calyx. o Renal pelvis: Major calyces unite to form the renal pelvis, a funnel-shaped structure that collects urine from the entire kidney. o Ureter: The renal pelvis narrows to form the ureter, a muscular tube that transports urine from the kidney to the bladder. A renal lobe is a structural unit of the kidney that includes a renal pyramid and the associated cortex. Human kidneys have approximately 10-20 lobes. The renal cortex can be further subdivided into renal lobules. Each lobule consists of a central medullary ray (pars radiata) and a surrounding cortical labyrinth (pars convoluta). o Medullary rays: Medullary rays contain the straight portions of the proximal and distal tubules and the collecting ducts. They appear as striations extending from the medulla into the cortex. o Cortical labyrinth: The cortical labyrinth surrounds the medullary rays and contains the renal corpuscles and the convoluted portions of the proximal and distal tubules. The blood supply to the kidneys is highly organized and follows a specific pathway: o Renal artery: The renal artery enters the kidney at the hilum and branches into segmental arteries. o Segmental arteries: Segmental arteries further divide into interlobar arteries, which travel between the renal pyramids within the renal columns. o Arcuate arteries: At the junction of the cortex and medulla, interlobar arteries branch into arcuate arteries, which arch along the base of the renal pyramids. o Interlobular arteries: Arcuate arteries give rise to interlobular arteries, which travel radially through the cortex toward the capsule. o Afferent arterioles: Interlobular arteries give off afferent arterioles, which supply the glomerular capillaries of the renal corpuscles. The renal veins follow a similar pathway in reverse, ultimately draining into the renal vein, which exits the kidney at the hilum. Chapter 35: Renal Tubules Jefferson E. Flores, MAEd, RN, LPT Assistant Professor Medical biology  Pointers for the Final Examination in MB105 The renal tubules are a series of tubular segments that modify the glomerular filtrate produced in the renal corpuscle, ultimately forming urine. They are responsible for reabsorbing essential substances back into the blood and secreting waste products and excess ions into the tubular fluid. The renal tubules can be divided into several segments based on their location and function: o Proximal convoluted tubule (PCT): The PCT is the longest and most convoluted segment of the renal tubule. It is located in the cortical labyrinth and is responsible for the reabsorption of approximately 65% of the filtered water, sodium, glucose, and amino acids. The PCT also secretes substances, such as **hydrogen ions Jefferson E. Flores, MAEd, RN, LPT Assistant Professor Medical biology