Lecture 24 Flashcards
Primary function of digestive system
Supply nutrients from food to blood -> cells
Processes enabling digestive syst to work are
- Ingestion
- Propulsion
- Mechanical digestion
- Chemical digestion
- Absorption
- Defecation
2 main categories of digestive system
- GI tract
- Accessory structures
GI tract is
Tube open at both ends for transit of food during processing
GI tract includes
Mouth
Esophagus
Stomach
Small/large intestines
Accessory structures do what
Contribute to food processing
Accessory structures include
Teeth
Tongue
Salivary glands
Liver
Gallbladder
Pancreas
Mechanical digestion is
Physical breakdown of food
Two sites of mechanical digestion
- Mouth
- Stomach (most happens in it)
Mouth mechanical digestion
Teeth/tongue breakdown food in smaller pieces by chewing, grinding, cutting, mixing etc (mastication)
Stomach mechanical digestion
Contraction of various layers of smooth muscle grind food in smaller pieces, help mix food with acidic gastric juices
Chemical digestion is
Chemical breakdown of larger into smaller molecules using enzymes
Reason for chemical digestion
Intestinal lining can only absorb very small molecules
Locations of chemical digestion
- Mouth
- Stomach
- First section of small intestine (duodenum)
Mouth chemical digestion
Digestive enzyme in saliva (amylase) that breaks down carbs into smaller sugars
Stomach chemical digestion
Enzyme in gastric juices (pepsin) breaks down prots into amino acids
Duodenum chemical digestion
Food chemically broken down by pancreas secreted enzymes (majority of chem digestion occurs here)
Esophagus is
Long tube of smooth muscle from larynx to stomach that moves food from mouth to stomach
Act of swallowing causes
Epiglottis to rise and block food entry to trachea
Stomach
Primarily smooth muscle, contraction physically breaks food (mechanical) and pepsin chemically breaks down prots
Gastric juice in stomach made of
Pepsin and acid
Small intestine
Longest portion of gi, 3 subdivisions, chemical digestion in duodenum (using enzymes from pancreas)
after duodenum, main function is allow small nutrients to cross into bv (absorption) to transport to cells
Liver main role in digestive system
Secrete bile into duodenum
Bile’s main role
Help break globs of fat into smaller droplets so easier for pancreatic enzymes to chemically break down into fatty acids
Gallbladder
Muscular sac storing excess bile, releases extra bile when eat food very fatty
Fat is hydrophobic so tends to stick together, bile basically
Forces fat molecules apart
Since small intestines function is absorption, mucosa structured to
Increase surface area (more contact with substances)
How is small intestine surface area increased
Walls folded into villi, which have cells (columnar epithelium) with microvilli lining each villus
Large intestine receives
Substances not absorbed by small (cannot be broken down/digested/absorbed, so excreted)
Major roles of large intestine
- Absorbs as much water as it can from unabsorbed material
- Prepare this material for excretion
Rectum (last segment of large intestine)
When material enter rectum, referred to as feces, where feces are stored until evacuation
Composition of water of feces
75% (despite large water amount absorbed by large intestine)
Other substances found in feces
- Bacteria (mostly from gut microbiota)
- Indigestible material (ex dietary fiber/cellulose)
- Fat (can be high after fat meals or lack of bile production)
- Cholesterol
Urinary system primary functions
- Removal of waster products from blood
- Blood volume regulation and water balance
Urinary syst secondary functions
- Storage of urine (bladder)
- Excretion of urine (via urethra)
Urinary syst includes
- 2 kidneys (filter blood/create urine)
- 2 ureters (bring urine from kid to bladder)
- Urinary bladder (storage)
- Urethra (allows urine excretion)
Urethra male vs female
Longer in male passes through penis, base surrounded by prostate
What is a nephron
Microscopic tubes in kidneys
Nephrons do what
- Each removes portion of waste from blood
- Getting rid of any excess water in body
- Fluid leaving a nephron is waste and water, called urine
How does the urge to urinate occur
When walls of bladder stretch to a certain point, signal sent to cortex
