Nephron Functions and Physiology Quiz

MPharm Programme Renal - PHA115

• The lecture is part of the MPharm Programme, specifically focusing on the renal system.
• The course code is PHA115.
• The presenter is Dr Praveen Bhugra.
• The university is Sunderland.

Learning Objectives

• Students will be able to describe the organs and function of the urinary system briefly.
• Detailed knowledge of kidney anatomy, including location, internal and external structure, blood and nerve supply, and function, will be acquired.
• The structure of the nephron and its blood supply, along with its function, will be understood.
• The lecture will delve into renal physiology, including urine formation, glomerular filtration, tubular reabsorption, tubular secretion, hormonal regulation, and homeostasis.

Urinary System

• The kidneys produce urine and help regulate bodily fluids.
• The ureters transport urine to the bladder.
• The urinary bladder acts as a reservoir for urine.
• The urethra carries urine to the exterior.

Urinary System (Specific Organs)

• Kidneys: paired, bean-shaped organs located along the back body wall, below the diaphragm, and adjacent to the vertebral column.
• Right kidney is slightly lower than the left due to the liver's position.
• Other Organs: ureters, urinary bladder, urethra are listed and their general functions are detailed.

Structure of Kidney

• The kidney comprises renal cortex, renal medulla, renal columns, renal pyramids, renal papilla, and renal capsule.
• The image shows the path of urine drainage, including minor and major calyxes, renal artery, renal pelvis, renal vein, ureter, and urinary bladder.

Blood and Nerve Supply

• ~1200 ml of cardiac output is delivered to the kidneys every minute via renal arteries.
• Arterial and venous blood flow through similar pathways.
• The nerve supply to the kidneys is via sympathetic fibers of the renal plexus.

Blood Supply of Kidney

• The detailed blood supply of the kidney is described, highlighting the renal artery, segmental arteries, interlobar arteries, arcuate arteries, cortical radiate arteries, afferent arterioles, glomerulus, efferent arterioles, peritubular capillaries, vasa recta, arcuate veins, interlobar veins, cortical radiate veins, and renal vein.

Renal Blood Supply

• The detailed pathway of blood flow from aorta to the peritubular capillaries and vasa recta, detailing renal artery, segmental artery, interlobar artery, arcuate artery, cortical radiate artery, afferent arteriole, glomerulus (capillaries), efferent arteriole, peritubular capillaries and vasa recta, interlobar vein, arcuate vein, cortical radiate vein, and renal vein.

Functions of the Kidney

• The kidney removes toxins, metabolic wastes, and excess ions from the blood.
• It regulates blood volume, chemical composition, and pH.
• Gluconeogenesis occurs during prolonged fasting.
• Endocrine functions include renin regulation of blood pressure and kidney function, erythropoietin regulation of RBC production, and vitamin D activation.

Functions of the Kidney (Calcium Homeostasis)

• The kidney regulates calcium and phosphate levels involving calcitriol, phosphate excretion, bone resorption, serum phosphate, and parathyroid hormone (PTH).
• The details of the regulation are shown in an image.

Nephron

• Nephrons are the structural and functional units of the kidney, responsible for forming urine.
• Approximately one million nephrons exist per kidney.
• Each nephron consists of a renal corpuscle (initial filtering component) and a renal tubule extending from the renal corpuscle.
• Detailed illustrations displayed show components of the nephron, like glomerular capsule, glomerulus, proximal convoluted tubule, loop of Henle, and distal convoluted tubule.
• Differences between cortical and juxtamedullary nephrons are described.

Nephrons (Cortical and Juxtamedullary)

• Cortical nephrons make up about 80-85% of the nephrons, with short loops of Henle and renal corpuscles located in the outer cortex.
• Juxtamedullary nephrons constitute the remaining 15-20%, situated deeper in the cortex near the medulla, with long loops of Henle extending deep into the medulla.
• Blood supply for each type differs slightly.

Nephrons (Collecting Duct)

• Distal convoluted tubules of multiple nephrons empty into a single collecting duct.
• These collecting ducts merge to create several hundred large papillary ducts, which drain into the minor calyces, major calyces, renal pelvis, and ureters.

Functions of the Nephron

• The process of filtering, reabsorbing, and secreting substances is described.
• These steps involve filtration from blood (plasma) into nephron, tubular reabsorption (fluid back into blood), and tubular secretion (from blood into fluid).
• Images illustrate these steps and their location within the nephron.

Renal Corpuscle

• The glomerular (Bowman's capsule), including its parietal and visceral layers, glomerulus (capillaries), mesangial cells, and their location relative to afferent and efferent arterioles, are described.

Glomerular Filtration

• Components of the filtration membrane are described, including the capillary endothelium, basement membrane, and foot processes of podocytes.
• The process of blood filtration is described and visualized to filter substances into the filtrate.
• Data on filtration rates and amounts of various substances (water, proteins, glucose, urea, creatinine) filtered, reabsorbed, and excreted by the kidneys is presented in tabular format.

Glomerular Filtration Regulation

• The role of two hormones, angiotensin II, and the atrial natriuretic peptide (ANP) in regulating glomerular filtration rate (GFR) are detailed.
• ANP actions are presented, which include relaxation of the glomerulus and increasing the filtration surface area.

Reabsorption Routes

• Detailed description of transcellular and paracellular pathways for reabsorption.
• Components like tight junctions and the basal membrane are described.
• Active and passive transport mechanisms involved in reabsorption are detailed.

Reabsorption in PCT and Other Tubular Segments

• Different substances' reabsorption occurs in distinct ways.
• The proximal convoluted tubule (PCT) reabsorbs water, Na+, various ions, amino acids, glucose through various symporters and channels.
• The thick ascending limb of the Loop of Henle regulates Na+, Cl-, and K+.

Reabsorption in Distal Convoluted Tubule and Collecting Duct

• Reabsorption of Na+ and secretion of K+ is described and related to principal cells.
• How this process is regulated by hormones is included

Hormones and Homeostasis

• Multiple hormones that impact sodium, chloride, calcium, water reabsorption and potassium secretion in the tubules are detailed.
• These hormones are crucial for maintaining homeostasis of blood flow, blood pressure, and volume.
• The actions of antidiuretic hormone (ADH), aldosterone, atrial natriuretic peptide (ANP). and parathyroid hormone (PTH) are detailed.
• This section presents a flowchart of how hormones regulate systemic blood pressure and the associated changes in GFR, using dehydration, blood volume decrease, and blood pressure decrease as triggers.

Test your knowledge on the functions and anatomy of nephrons, focusing on the distinctions between juxtamedullary and cortical nephrons. This quiz covers key concepts such as blood supply, filtration rates, and the roles of various nephron components. Perfect for students of renal physiology and advanced biology!