Pancreas, Kidney, and Adrenal Glands

• These notes cover the pancreas, kidney function, adrenal glands, and blood vessels of the kidney, as well as their key functions and structures.

Location of the Pancreas

• The pancreas is located behind (posterior) to the stomach
• It stretches from the duodenum to the spleen
• The pancreas is attached to the posterior abdominal wall
• It is covered by a thin connective tissue capsule

Functions of the Pancreas

• The pancreas has both endocrine and exocrine functions

Endocrine Function

• Endocrine cells in the Pancreatic Islets (Islets of Langerhans) produce hormones
• Insulin lowers blood sugar levels
• Glucagon raises blood sugar levels

Exocrine Function

• Exocrine cells, consisting of Acinar cells and duct epithelial cells, produce enzymes
• The pancreas secretes pancreatic juice (digestive enzymes and bicarbonate)
• This juice helps digest proteins, fats, and carbohydrates in the small intestine

Pancreatic Enzymes

• Pancreatic Alpha-Amylase is a carbohydrase that breaks down carbs into starches
• It produces simple sugars like maltose
• Similar to salivary amylase, it continues carbohydrate breakdown that starts in the mouth
• Pancreatic Lipase is a lipase that breaks down fats
• It breaks down complex lipids (fats) into fatty acids and monoglycerides, which are easily absorbed
• It works with bile to digest fats in the small intestine
• Nucleases are enzymes that break down nucleic acids
• They break down DNA/RNA into nucleotides (building blocks of nucleic acids)
• Proteolytic enzymes include proteases and peptidases
• Proteases break large proteins into smaller parts
• Peptidases break small peptides into amino acids
• 70% of pancreatic enzyme production is for protein digestion

Main Functions of the Kidneys

• Kidneys filter blood
• They remove waste
• Kidneys maintain fluid, electrolyte, and pH balance
• They regulate blood pressure and red blood cell production

Filtration in the Kidneys

• Filtration occurs in the glomerulus (part of the nephron)
• Blood enters the glomerulus under pressure
• Water, ions, glucose, and small molecules are filtered out of the blood into Bowman's capsule
• Blood cells and proteins stay in the bloodstream because they are too large to filter

Secretion in the Kidneys

• Secretion mainly occurs in the distal convoluted tubule and collecting duct
• The body actively transports waste (like H+, K+, ammonia, drugs) from the blood into the nephron
• Secretion helps maintain pH balance and remove toxins.

Reabsorption in the Kidneys

• Reabsorption mainly occurs in the proximal convoluted tubule, loop of Henle, distal tubule, and collecting duct
• The nephron reabsorbs useful substances (like glucose, amino acids, water, and salts) back into the blood
• Reabsorption prevents the loss of essential nutrients
• It is controlled by hormones like ADH (water reabsorption) and aldosterone (Na+ reabsorption)

Adrenal Glands

• Two small glands sit on top of each kidney
• They help control stress, energy, blood pressure, and metabolism
• The adrenal cortex (outer layer) makes steroid hormones

Cortisol

• Cortisol ("Stress Hormone") helps the body handle stress
• It controls blood sugar and reduces inflammation

Aldosterone

• Aldosterone ("Salt & Water Balance") controls blood pressure by regulating sodium & potassium

Adrenal Medulla

• The adrenal medulla (inner layer) mediates the fight or flight response
• Adrenaline (Epinephrine) increases heart rate, breathing, and energy when stressed

Peritubular Capillaries

• They surround the proximal and distal tubules of the nephron, mainly in the cortex of the kidney
• They help with reabsorption and secretion
• These capillaries take back useful substances like water, glucose, and salts into the blood
• They let go of waste or extra substances (like H+, drugs) into the nephron

Vasa Recta

• Vasa Recta surrounds the Loop of Henle (in juxtamedullary nephrons, deeper in the kidney)
• They help maintain the concentration of urine
• These vessels work with the loop to reabsorb water and keep the body from losing too much
• They are important for creating concentrated urine (when you're dehydrated)

Glomerulus

• A tiny ball of capillaries is inside the Bowman's capsule
• Its main job is to filter blood to form urine

Afferent Arteriole

• The afferent arteriole ("Arriving") brings blood into the glomerulus
• The blood is under high pressure to push fluid into Bowman's capsule
• It is larger than the efferent arteriole to create pressure

Efferent Arteriole

• The efferent arteriole ("Exiting") takes blood away from the glomerulus
• Blood has been filtered
• It leads to peritubular capillaries or vasa recta for further processing

Filtration in the Glomerulus

• Water, glucose, salts, and urea pass into Bowman's capsule
• Blood cells and proteins stay in the bloodstream because they are too big to filter

Nephron Structure

• A nephron is the basic filtering unit of the kidney
• Each kidney has about 1 million nephrons

Bowman's Capsule

• A cup-shaped structure surrounds the glomerulus
• It collects the filtered fluid (filtrate) from the blood

Glomerulus (Nephron)

• A bundle of capillaries is inside the Bowman's capsule
• It is where blood is filtered

Proximal Convoluted Tubule (PCT)

• A twisty tube is right after the Bowman's capsule
• It reabsorbs nutrients, water, and salts back into the blood

Loop of Henle

• A long loop dives into the kidney medulla
• The descending limb reabsorbs water
• The ascending limb reabsorbs salts (Na+, Cl-)

Distal Convoluted Tubule (DCT)

• Another twisty tube helps with secretion (removes more waste like H+, drugs)
• It also fine-tunes salt and water balance

Collecting Duct

• This duct collects urine from many nephrons
• Reabsorbs water (controlled by ADH)
• It sends urine to the renal pelvis, then the ureter, and finally the bladder

Blood Supply Around the Nephron

• The Afferent arteriole brings blood into the glomerulus
• The Efferent arteriole takes filtered blood out
• It leads to Peritubular capillaries (around tubules) and Vasa recta (around the loop of Henle in juxtamedullary nephrons)

Key Functions and Components of the Kidney

• Glomerulus filters blood
• Bowman's Capsule catches the filtrate
• PCT reabsorbs water, glucose, and salts
• Loop of Henle reabsorbs water & salts
• DCT secretes waste and fine-tunes balance
• Collecting Duct reabsorbs water and forms final urine

Additional Notes

• Glycosuria indicates glucose in the urine and may indicate high blood sugar or diabetes
• Proteinuria indicates protein (albumin) in the urine and may indicate kidney damage, disease, or infections
• Cells in urine indicate something is wrong with the kidneys or urinary tract
• Cortex is the outer part of the kidney
• Medulla is the inner part of the kidney
• The medulla is hypertonic, meaning it has a high concentration of solutes, especially sodium (salt)

Arteriole Bloodflow

• Afferent arteriole bringing oxygenated blood to get filtered
• Efferent arteriole carrying partially deoxygenated blood away
• Kidney's nephrons acts like second endocrine gland secreting hormones

Summary of the Kidney's Activities

• Cortex less concentrated
• Medulla more concentrated = hypertonic
• Nephron the filtering unit responsible for filtering blood and forming urine

Kidney Functions

• Filter waste products and excess substances (like water, salts, and urea) from the blood to form urine
• Control blood pressure by adjusting the volume of water and sodium in the body and secreting renin
• Maintain the acid-base balance by secreting hydrogen ions (H+) and reabsorbing bicarbonate (HCO3) Regulate the levels of sodium, potassium, calcium, and phosphate in the blood
• Produce erythropoietin (EPO), which stimulates the bone marrow to produce red blood cells in response to low oxygen levels.
• Convert inactive vitamin D into its active form (calcitriol), which helps with calcium absorption in the intestines and bone health.
• Excrete toxins, drugs, and metabolic waste products like urea and creatinine through urine.