Essentials of BiologySylvia S. Mader

Chapter 24Lecture Outline

Prepared by: Dr. Stephen EbbsSouthern Illinois University Carbondale

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

24.1 Digestive System

• There are three organ systems in the body that facilitate the exchange of gases, nutrients, and wastes with the cells and fluids of the body.– Digestive system– Respiratory system– Urinary system

• The activity of these systems helps the body maintain homeostasis.

Tube-Within-a-Tube Body Plan

• The digestive systems of most animals is a complete tube-within-a-tube, meaning that it has a mouth and anus.

• This inner tube is separated from the body wall by the coelom.

• The basic plan for the digestive system is similar across animal species.

Tube-Within-a-Tube Body Plan (cont.)

Tube-Within-a-Tube Body Plan (cont.)

• The digestive system of animals performs four essential functions.– Ingests food– Breaks down food into smaller molecules– Absorbs nutrients in molecules– Eliminates indigestible waste

Mouth

• For most animals, the digestive tract begins with the mouth.

• While teeth mechanically tear and grind food, the salivary glands release the enzyme amylase into the mouth to degrade carbohydrates.

• The ground, partially-digested food material that is swallowed is called a bolus.

Swallowing

• In many animals, the digestive and respiratory systems share a common passage behind the mouth called the pharynx.

• The flow of food through the pharynx and into the esophagus is assisted by the epiglottis, which covers the respiratory passage.

• The rhythmic contractions of the esophagus, called peristalsis, move food to the stomach.

Swallowing (cont.)

Stomach

• The stomach is the organ in which proteins in food are digested.

• The low pH of the stomach and the presence of the enzyme pepsin accomplish the digestion of proteins.

• Peristalsis moves food through the stomach while a sphincter regulates the flow of digested food into the intestine.

Stomach (cont.)

Stomach (cont.)

• Ruminant is a term used to describe animals like cattle that have a stomach with a compartment called the rumen.

• The rumen contains symbiotic bacteria that help these herbivores digest plants.

• When animals chew cud, they are chewing the partially-digested rumen product.

Stomach (cont.)

Small Intestine• The digested food material the exits the stomach

and enters the small intestine is called chyme.

• The small intestine provides two functions.– Additional digestion of food material– Absorption of nutrients

• Three additional organs that assist the small intestine.– Liver– Gallbladder– Pancreas

Small Intestine (cont.)

• The liver produces bile to emulsify fats for digestion and absorption.

• Excess bile is stored in the gallbladder.

• The pancreas produces a juice that contains substances that enhance digestion.– Sodium bicarbonate, to increase chymal pH– Pancreatic enzymes

Small Intestine (cont.)

• There are several pancreatic enzymes.– Pancreatic amylase to digest starches– Trypsin to digest proteins– Lipase to digest fats– Nuclease to digest nucleic acids

• Absorption of the digested nutrients is facilitated by hair-like villi in the intestine.

• The villi have microvilli to greatly increase their surface area for absorption.

Small Intestine (cont.)

Small Intestine (cont.)

Large Intestine

• The large intestine absorbs water, salts, and some vitamins.

• The appendix is a pouch of the large intestine.

• Bacteria in the large intestine digest remaining material prior to excretion of the wastes (feces) through the anus.

Pancreas

• The pancreas functions as both an endocrine and exocrine gland.

• The endocrine function of the pancreas involves secretion of insulin and glucagon into the bloodstream.

• The exocrine function of the pancreas involves the secretion of pancreatic juice into the small intestine.

Liver

• The liver has a variety of functions.– Removal of poisons and toxins from the blood– Production of plasma proteins– Destruction of old red blood cells– Production of bile– Storage of glucose as glycogen– Production of urea, a nitrogenous waste

• The liver functions are carried out as blood from the intestines travels to the liver through the hepatic portal system.

Liver (cont.)

Liver (cont.)

• Disorders of the liver can have a significant effect on human health.– Jaundice occurs when there is an excessive

concentration of bile pigments in the blood.

– Hepatitis is a viral infection of the liver.– During cirrhosis, liver tissue changes to

become fatty and then non-functional scar tissue.

24.2 Respiratory System

• The respiratory system allows for the exchange of gases between the blood and the external air.

• Animal respiration involves three steps.– The inspiration (inhalation) and expiration (exhalation)

of breathing– External gas exchange between the air and blood

within the lungs– Internal gas exchange between the blood and body

fluids

24.2 Respiratory System (cont.)

The Human Respiratory Tract

• The human respiratory system includes the lungs and all structures that move air to and from the lungs.

• The respiratory tract is lined with cilia to filter debris and dust.

• The air flowing through the respiratory system is also warmed to body temperature and saturated with water.

The Upper Respiratory Tract

• The upper respiratory tract consists of three structures.– Nasal cavities and the interconnected sinuses– The pharynx – The larynx, or voice box, and the vocal cords

• The tonsils are lymphatic tissue at the junction between the mouth and pharynx.

• The glottis is the opening between the pharynx and larynx.

The Upper Respiratory Tract (cont.)

Lower Respiratory Tract

• The respiratory tract consists of the respiratory tree.– The trachea, or windpipe– The primary bronchii leading to each lung– The smaller, branching bronchioles within

each lung– The sac-like alveoli at the end of each

bronchiole where gas exchange occurs

Breathing

• All terrestrial vertebrates except birds breathe due to the contraction of the diaphragm.

• Contraction of the diaphragm creates a negative pressure that causes inspiration.

• Relaxation of the diaphragm causes expiration.

• The method of breathing creates a bi-directional, reversible flow of air.

Breathing (cont.)

Breathing (cont.)

• In birds, the ventilation of the lungs is a one-way path.

Lungs and External Exchanges of Gases

• The branching of the bronchioles and numerous alveoli of the lungs provide a large surface area for gas exchange.

• The alveoli are in close contact with blood vessels, forming the respiratory membrane which facilitates gas exchange.

• Emphysema is a lung condition that occurs when the alveolar walls have been damaged.

Lungs and External Exchanges of Gases (cont.)

Lungs and External Exchanges of Gases (cont.)

Lungs and External Exchanges of Gases (cont.)

• Aquatic animals use gills to facilitate gas exchange.

• The gills have an extensive capillary network that directly exchanges gases with water flowing over the gills.

Lungs and External Exchanges of Gases (cont.)

Transport and Internal Exchange of Gases

• It is the heme group of the hemoglobin in red blood cells that carries oxygen.

• Hemoglobin acquires oxygen as the blood flows through the vessels surrounding the alveoli.

• Several factors can trigger the release of oxygen from hemoglobin.– A decrease in the oxygen concentration in the tissues– Increased temperature– Decreased pH

Transport and Internal Exchange of Gases (cont.)

• Carbon dioxide is carried in the blood as dissolved bicarbonate (HCO3

-).

• When the blood passes through the vessels surrounding the alveoli, the carbon dioxide diffuses into the alveoli for expiration.

• The breathing center of the brain regulates the rate of breathing by monitoring blood pH.

Transport and Internal Exchange of Gases (cont.)

24.3 Urinary System and Excretion

• The mammalian kidney serves several important functions.– Excretion of nitrogenous wastes– Maintenance of water-salt balance of blood– Maintenance of the blood pH

• The urine made by the kidneys passes through the ureter to the urinary bladder, where it is stored prior to excretion through the urethra.

24.3 Urinary System and Excretion (cont.)

Kidneys

• The kidney has three main regions.– The renal cortex is the outer region.– The renal medulla lies underneath the cortex.– The renal pelvis is the innermost layer.

• The urine-producing cells that make up the kidney are called nephrons.

Kidneys (cont.)

Nephrons

• Nephrons have several parts which contribute to the formation of urine.– The nephron capsule, which allows for the

diffusion of molecules from the blood– The proximal tubule, tightly packed with

microvilli– The nephron loop, which has a descending

and ascending limb– The distal tubule– The collecting duct

Urine Formation

• There are three steps in urine formation.– During filtration, small molecules pass from

the blood into the nephron capsule.– Nutrients and other molecules move back to

the blood during reabsorption.– During secretion, wastes are selectively

transported into the distal tubule.

Urine Formation (cont.)

Problems with Kidney Function

• A variety of human illnesses are associated with kidney problems.– Renal disease and failure can be caused by

hypertension or diabetes.– Kidney stones can form from pH imbalances,

excess Ca, or urinary tract infections.– Edema (build up of fluid) can occur if too

many nephrons are blocked or are not functioning.

Hemodialysis and Kidney Replacement

• Patients with renal failure may require hemodialysis to filter their blood.– Artificial kidney machines

– Continuous ambulatory peritoneal dialysis

• In extreme situations, it is necessary to replace the damaged kidney with a transplant.

Hemodialysis and Kidney Replacement (cont.)