Zoology Digestive Systems Overview

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Questions and Answers

What is the primary function of the digestive system?

To filter waste from the blood

To produce hormones for growth

To transport oxygen throughout the body

To break down food into molecules (correct)

Which process initiates mechanical digestion?

Swallowing food into the esophagus

Contraction of the stomach

Chewing food with teeth (correct)

Chemical breakdown by enzymes

What role does bile play in digestion?

It is primarily responsible for protein breakdown

It acts as a coagulant for food particles

It breaks down carbohydrates into sugars

It helps in the digestion of lipids (correct)

Which of the following describes peristalsis?

Contraction of circular muscles to move food Signup and view all the answers

What is the initial site of chemical digestion?

Mouth Signup and view all the answers

What are the simplest forms of food absorbed after digestion?

Glucose, amino acids, and fatty acids Signup and view all the answers

Which enzyme is responsible for carbohydrate digestion in the mouth?

Amylase Signup and view all the answers

What is the primary role of catabolic processes in metabolism?

Breaking down molecules for energy Signup and view all the answers

What process involves the reabsorption of amino acids and glucose into the blood?

Secondary active transport Signup and view all the answers

Which waste products are disposed of by the kidneys?

Urea, creatinine, ammonium, and uric acid Signup and view all the answers

Which enzyme is secreted by the pancreas for lipid digestion?

Lipase Signup and view all the answers

What is the main function of the urinary system?

Regulate blood composition and volume Signup and view all the answers

Which of the following is NOT a function of anabolic processes?

Energy production Signup and view all the answers

What is the approximate volume of filtrate produced by the kidneys per day?

180 liters Signup and view all the answers

What is the net filtration pressure in the glomerulus?

10 mmHg Signup and view all the answers

Which of the following best describes the process of reabsorption in the Proximal Convoluted Tubule (PCT)?

Obligatory reabsorption of nutrients and electrolytes Signup and view all the answers

Which pressure opposes glomerular filtration?

Blood osmotic pressure Signup and view all the answers

At what blood glucose level does glucosuria begin to occur?

180 mg/dl Signup and view all the answers

Which of the following correctly states the amount of sodium and water reabsorbed in the PCT?

70% Signup and view all the answers

What is the permeability feature of the descending loop of the Loop of Henle?

Permeable to water Signup and view all the answers

What percentage of the filtrate is typically reabsorbed by the nephron?

99% Signup and view all the answers

Which of the following substances is a common waste product excreted in urine?

Urea Signup and view all the answers

What is the primary component of urine by volume?

Water Signup and view all the answers

How does alcohol affect urine production?

Inhibits secretion of ADH Signup and view all the answers

Which factor prevents excess loss of sodium and promotes water retention in the body?

Aldosterone Signup and view all the answers

What does dialysis do for patients with kidney failure?

Filters waste products from the blood Signup and view all the answers

During dialysis, how does passive diffusion occur?

From high to low concentration Signup and view all the answers

What daily urine output is considered oliguria?

500ml or less Signup and view all the answers

What is a potential consequence of untreated kidney failure?

Development of edema Signup and view all the answers

What is the primary function of the loop of Henle in the nephron?

It contributes to the concentration of tubular fluid. Signup and view all the answers

What determines the reabsorption in the distal convoluted tubule (DCT) and collecting tubule (CT)?

It is dependent on the body's needs and hormone regulation. Signup and view all the answers

How does ADH affect water reabsorption in the kidneys?

It increases water retention by facilitating its reabsorption. Signup and view all the answers

What is a significant effect of low levels of ADH in the body?

High urine volume and low urine concentration occur. Signup and view all the answers

What is the primary role of sodium pumps in the ascending loop of Henle?

To pump sodium and help in creating a concentration gradient. Signup and view all the answers

What is the relationship between the length of the loop of Henle and the ability to reabsorb water?

Longer loops increase reabsorption efficiency in hyperosmotic conditions. Signup and view all the answers

Which type of cells in the DCT and CT respond to ADH and aldosterone?

Cells endowed with specialized receptors. Signup and view all the answers

What is the process of selective transport from blood to the renal tubules called?

Secretion Signup and view all the answers

What is the typical blood pH level that must be maintained in the body?

7.4 Signup and view all the answers

Where are the kidneys located in the human body?

At the back of the abdomen, below the diaphragm Signup and view all the answers

What is the maximum capacity of an adult urinary bladder?

600 ml Signup and view all the answers

What is the primary function of the nephron in the kidneys?

To produce urine through filtration, reabsorption, and secretion Signup and view all the answers

What happens during the filtration step of urine formation?

Water and small molecules are removed from blood into the renal capsule Signup and view all the answers

What defines the Glomerular Filtration Rate (GFR)?

The amount of filtrate produced by the kidneys each minute Signup and view all the answers

How long can a typical healthy adult hold urine in their bladder?

9-10 hours Signup and view all the answers

Which kidney is located higher in the abdomen?

The left kidney Signup and view all the answers

Study Notes

Functioning Systems

The presentation is by Prof. Dr. Eman Salah Abdel-Reheim
The topic is Zoology.
The location of the presentation is Beni-Suef University.

Food Assimilation

Learning objectives include:
- General function of digestive system
- Mechanical & chemical digestion
- Simplest forms of nutrients & their absorption
- Simple outlines about metabolism

Functions of Digestive System

Breaks down food into molecules.
Absorbs molecules into blood for bodily distribution.
Eliminates wastes from the body.

Digestion

Digestion is the process by which the body breaks down food into small nutrient molecules.
It begins in the mouth.

Types of Digestion

Mechanical digestion: physically breaks down food into smaller pieces, beginning with chewing. The process includes mastication (chewing) and teeth cutting.
Chemical digestion: breaks down food into smaller chemical building blocks using chemicals produced by the body. This begins in the mouth.

Mechanical Digestion Expressions

Mastication: chewing and enzymatic breakdown by saliva.
Deglutition: swallowing; voluntary in the mouth, involuntary in the esophagus.

Mechanical Digestion

Churning in the stomach forms chyme.
Peristalsis: contraction of circular muscle.
Segmentation: contraction of longitudinal muscle (back and forth movement) till the colon.

Chemical Digestion: Digestive Juices

Saliva: from parotid, sublingual, & submandibular glands.
Gastric: chief cells for pepsinogen, parietal cells for HCl.
Pancreatic: from exocrine cells in the pancreas.
Bile: produced by the liver, stored in the gall bladder, secreted into the small intestine for lipid digestion.
Intestinal Juice: secreted by the mucosa of the small & large intestines.

Chemical Digestion

accomplished by enzymes :
- Mouth (carbohydrates): salivary amylase
- Stomach (proteins): pepsin
- Small intestine (lipids): trypsin, chymotrypsin, amylase, and lipase
- Small intestine (carbohydrates, proteins, and lactose) : maltase, sucrase, lactase, and peptidases from intestinal villi.

Absorption

After digestion, the simplest forms of food (glucose, amino acids, and fatty acids) are absorbed.
Absorption is the passage of these nutrients through the intestinal mucosa into the blood.
- Amino acids & glucose are absorbed into the blood by secondary active transport.
- Fatty acids enter the lymph via simple diffusion.

Metabolism

Catabolism:
- Hydrolysis: breaks down monomers.
- Cellular respiration: oxidizes monomers to yield energy
Anabolism:
- Cell maintenance & repair
- Growth
- Formation of secretions
- Nutrient reserves

Metabolic Processes of Substances

Glucose: glycolysis, Kreb's cycle, electron transport chain, Glycogenesis, gluconeogenesis
Fatty acids: beta-oxidation, Kreb's cycle, electron transport chain, lipogenesis
Amino acids: deamination, Kreb's cycle, electron transport chain, synthesis of non-essential amino acids

Urinary System

Learning objectives include:
- Functions of the urinary system
- Anatomy of the urinary system
- Nephron structure
- Urine formation: Filtration, Reabsorption, Secretion
- Urine composition
- Factors affecting kidney function
- Hemodialysis

Function of the Urinary System

Regulates blood composition and volume to maintain homeostasis.
- Disposes of metabolic waste (urea, creatinine, ammonium, uric acid).
- Maintains water-salt and electrolyte balance (sodium, potassium, bicarbonate, etc.).
- Maintains acid-base balance (blood pH ~7.4).

Structure & Anatomy of the Urinary System

Kidneys: located in the back of the abdomen, one on each side just below the diaphragm
- The left kidney is located in the T12 to L3 vertebrae and the right kidney is lower due to liver displacement.
- Each kidney weighs about 125-175 g in males and 115-155 g in females.
- Approximately 11-14 cm in length, 6 cm wide, and 4 cm thick.
- Uses 20-25% of the body’s oxygen
Ureters: 25 cm long muscular tubes that carry urine from the kidneys to the bladder.
Bladder: a triangle-shaped hollow organ in the lower abdomen, storing urine. Urine empties through the urethra.
Urethra: a tube that carries urine out of the body.

Kidney Anatomy

The kidney is protected by fibrous tissue, fat, muscle, and ribs.
Consists of the outer renal cortex and inner medulla then pelvis. Renal cortex, Renal medulla, Renal papilla, Renal pyramid, Renal artery, Renal pelvis, Minor calyx, Major calyx, Renal vein, Bowman's capsule, Collecting duct, Nephron

Nephron

The structural and functional unit of the kidney, composed of the renal corpuscle and renal tubules.
- Renal corpuscle: glomerular capsule (cup-shaped) and capillary network (glomerulus)
  - Proximal convoluted tubule (PCT), Nephron loop (Loop of Henle), Distal convoluted tubule (DCT)

Steps in Urine Formation

Filtration: water and small molecules are removed from the blood into the renal capsule (pressure filtration, depends on size).
Reabsorption: water and essential molecules are returned to the blood in the renal tubules.
Secretion: wastes and excess salts are added from body fluids to tubular fluid (urine) in the renal tubules.

Glomerular Filtration Rate (GFR)

The amount of filtrate produced by the kidneys each minute.
- 20% of total blood enters each kidney every minute (~1000 -1200 ml/min).
- ≈625 ml of plasma only pass as filtrate.
  - Only approx. 20% of the filtrate passes into the tubules.
  - 125-130 ml of the filtrate passes through the renal tubules (~180 liters/day).
- The kidneys can filter ~150-200 liters of plasma per day.

Forces Affecting Filtration

Glomerular capillary hydrostatic pressure (GHP) = +55 mmHg
Blood osmotic (colloidal) pressure (BOP) = -30 mmHg
Capsular hydrostatic pressure (CHP) = -15 mmHg
Net filtration rate = +10 mmHg

Reabsorption

Reabsorption of nutrients, electrolytes, and water occurs through mechanisms in the renal tubules.
- Proximal Convoluted Tubule (PCT)
- Loop of Henle
- Distal Convoluted Tubule (DCT)

PCT- Reabsorption ("Obligatory Reabsorption")

Glucose and amino acids are pumped out of the tubules by secondary active transport.
The transporter for glucose has a limited capacity.
If blood glucose is above 180 mg/dL, glucose remains in the urine (glucosuria).

PCT- Reabsorption

70% of sodium and water are reabsorbed.
Water moves into the peritubular space by osmosis (passively).
Chloride follows sodium by simple diffusion.
Some compounds present in high concentration in filtrate but low in blood can move through diffusion.

Loop of Henle- Reabsorption

Descending loop: permeable to water, moves water out of the tubules down the osmotic gradient. NO sodium pumps.
Ascending loop: thick epithelium, impermeable to water but has many sodium pumps.

So, why is the loop of Henle useful?

The longer the loop, the deeper it travels into the hyperosmotic medulla; more reabsorption and more concentrated tubular fluid is formed
The collecting tubule runs through the hyperosmotic medulla for greater ability to reabsorb H2O.

DCT and CT Reabsorption ("Facultative Reabsorption")

Reabsorption here depends on the body's need
- DCT & CT walls have tight junctions, impermeable to water.
- The cell membrane has receptors able to bind and respond to hormones (ADH and aldosterone)
- The binding of hormones modifies the membrane permeability of water and ions based on need.

Regulation of ADH secretion

ADH increases water retention and reduces urine volume, prevents dehydration.
ADH regulates decreased blood volume and/or decreased blood pressure (BP), through baroreceptors in the cardiovascular system
ADH also regulates increased salt concentration via osmoreceptors in the hypothalamus to monitor extracellular osmolality changes. (Why?)

DCT and CT-Reabsorption (Urine Concentration)

Late distal tubule (impermeable to H2O) : :ADH is low → no binding → H2O is not reabsorbed
Late distal tubule (permeable to H2O) : ADH is released → binds to receptors → aquaporin channels open → H2O moves into the blood → low urine volume with high concentration

Secretion and Excretion

Secretion: Selective transport of molecules from blood in the peritubular capillaries to the lumen of renal tubules
Example of excreted waste products: urea, excess drug metabolites, K+, H+, Ca++
Excretion: the body removes urine; molecules are dumped outside the tubules.

Urine Formation Summary

Diagram illustrating the process of urine formation in the nephron
- Shows different stages of filtration, reabsorption, secretion, and excretion in the kidney

Urine Composition

Urine composition varies with time and reflects the amount of water and solutes eliminated by the kidneys to maintain homeostasis.
Urine is 95-96% water and contains urea, uric acid, traces of amino acids, and electrolytes.
Normal daily production is 600-2500 ml/day.

Factors that Affect Kidney Function

ADH: prevents excess water loss (less urine volume & concentrated urine)
Alcohol: inhibits ADH secretion (more urine volume & diluted urine)
Aldosterone: prevents excess sodium and water loss (less urine volume, no effect on urine concentration - why?)
Caffeine: increases rate of salt and water loss; blocks adenosine receptors
Increased blood pressure: increase rate of water loss

Notes

Kidney diseases affect structure and function in 5 stages (from normal function to failure)
Kidney failure is fatal if untreated.
Kidney failure is treated by dialysis or transplantation.
Kidney is the first successfully transplanted organ in humans (in 1954).

Hemodialysis

Dialysis is a treatment for people with kidney failure.
- The kidneys do not filter blood normally, causing waste and toxins to build up
- Dialysis removes waste products from the blood.
- The dialyzer separates blood from the dialysis solution using a thin membrane; passive diffusion between the blood and dialysate.
- Waste products are removed into the dialysate, while essential minerals and amino acids move from the dialysate to the blood.

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Description

Explore the vital functions of the digestive system in this quiz. Learn about mechanical and chemical digestion, nutrient absorption, and the metabolism processes. This content serves as a comprehensive guide for students studying zoology.