Bio -chapter 23 Flashcards
(20 cards)
Stomach
Muscular, stretchable organ that mixes food with gastric
fluid that it secretes
Gastric fluid
Fluid secreted by the stomach lining
Contains enzymes, hydrochloric acid, and mucus
Chyme
Mix of food and gastric fluid
Stomach Functions: Digestion begins in stomach
Three functions of the stomach:
Mixes and stores ingested food
Secretes substances that begin food breakdown
Helps control passage of food into the small intestine
Protein digestion starts in the stomach:
Gastric fluid unfolds proteins
Pepsin cuts proteins into polypeptides
Digestion in the Small Intestine
Digestion of all nutrients is completed in the small intestine
Most nutrients and fluid are absorbed across the wall of the
small intestine
Many folds and projections in the lining of the small intestine
increase surface area for digestion and absorption
Intestinal folds are covered with villi
Brush border cells at the villus surface have microvilli
Digestion in the Small Intestine
The small intestine receives chyme from the stomach, enzymes from the pancreas, and bile from the liver and gallbladder
Digestive enzymes from the pancreas break carbohydrates, proteins, fats, and nucleic acids down into subunits
Bile (salts, pigments, and cholesterol produced by the liver) aids fat digestion by keeping fat droplets from clumping together, providing greater surface area for digestion.
Between meals, the main bile duct from liver to small intestine is closed and bile enters the gallbladder, which stores it.
Absorption in the Small Intestine
Absorption is the passage of nutrients, water, salts, and vitamins into the cells lining the digestive tract.
Simple sugars and amino acids move through brush border cells, then enter a capillary
Triglycerides enter lymph vessels, which eventually carry them to blood
Concentrating and Eliminating Wastes
The large intestine
Receives material from the small intestine
Absorbs ions and vitamins made by bacteria living in the
colon
Concentrates undigested residues as feces, which are stored
in the rectum and expelled through the anus
Regulating Internal Fluids
Fluid homeostasis
Fluid outside cell: the extracellular fluid serves as the
body’s internal environment.
Eating and drinking add water and nutrients to extracellular fluid.
Metabolism adds wastes such as urea, a nitrogen- containing by-product of protein digestion.
Urinary system
gets rid of the unwanted solutes and excess water
Kidneys
filter water, mineral ions, nitrogen wastes and other substances from blood; return water and non-wastes to blood, and form urine
Urine
is a mix of water and soluble wastes formed and excreted by the urinary system
Ureters
Tubes that carry urine from kidneys to the bladder
Urinary bladder
Hollow, muscular organ that stores urine
Urethra
Tube which carries urine out of the body
Kidney Function
A renal artery carries blood to be cleansed to each kidney, and a renal vein transports cleansed blood away from it
Kidneys contain many nephrons which filter blood and form urine by three processes: filtration, reabsorption, and secretion
Filtration
Blood pressure forces water and small solutes out across the walls of
capillaries at the start of a nephron
Proteins and blood cells remain in the blood
Reabsorption
Water and essential solutes return to the blood (99%).
Wastes such as urea and degraded hemoglobin remain in the filtrate.
Degraded hemoglobin gives urine its yellow color.
Tubular secretion
H+ and other unwanted substances move out of capillaries and into the nephron for excretion. It maintains the acid-base balance.
Sphincter
a ring of muscle that controls passage of material through a tube. It opens to allow the food into the stomach and closed to prevent stomach acid from splashing to esophagus.
