PART 2 - Digestive system small intestines, liver, pancreas and colon

Pancreas

An accessory organ with both endocrine and exocrine functions that aids digestion and blood sugar regulation

Pancreatic acinar cells

Cells in the pancreas that produce digestive enzymes in pancreatic juice

Pancreatic duct

Tube that merges with the bile duct and releases pancreatic secretions into the duodenum

Hepatopancreatic sphincter

Muscle that controls release of pancreatic and bile secretions into the small intestine

Pancreatic enzymes

Include amylase, lipase, proteases (like trypsin, chymotrypsin), and nucleases

Trypsinogen

Inactive enzyme activated by enterokinase to form trypsin in the small intestine

Trypsin

Enzyme that digests proteins in the small intestine

Pancreatic amylase

Enzyme that breaks down carbohydrates into disaccharides

Pancreatic lipase

Enzyme that breaks down triglycerides into glycerol and fatty acids

Nucleases

Enzymes that digest nucleic acids (DNA and RNA) into nucleotides

Chymotrypsin and carboxypeptidase

Enzymes that break proteins into dipeptides

Secretin

Hormone that stimulates pancreas to release bicarbonate

Cholecystokinin (CCK)

Hormone that stimulates pancreas to release enzyme

Bicarbonate in pancreatic juice

Neutralizes stomach acid for enzyme activity in small intestine

Liver

Largest internal organ responsible for metabolism, detoxification, and bile production

Hepatic lobules

Hexagon

Hepatic portal vein

Brings nutrient

Kupffer cells

Specialized liver macrophages that perform phagocytosis

Hepatocytes

Liver cells that process nutrients, detoxify blood, and secrete bile

Bile

Yellow

Bile components

Water, bile salts, bile pigments, cholesterol, and electrolytes

Bile salts

Essential for emulsifying fats for digestion and absorption

Gallbladder

Stores, concentrates, and releases bile through the cystic duct

Cystic duct

Connects gallbladder to the hepatic duct

Common bile duct

Formed by union of cystic and hepatic ducts, leads to duodenum

Gallstone

Crystallized cholesterol that can block bile flow

Bile release regulation

Triggered by cholecystokinin when food enters duodenum

Emulsification

Process where bile salts break large fat droplets into small ones

Small intestine

Major site for digestion and nutrient absorption; divided into duodenum, jejunum, and ileum

Mesentery

Double layer of peritoneum that supports and supplies the small intestine

Intestinal villi

Finger

Microvilli

Tiny projections on epithelial cells that further increase absorption area

Lacteal

Lymphatic capillary in villus that absorbs dietary fats

Goblet cells

Secrete mucus to lubricate and protect intestinal lining

Intestinal glands

Secrete watery fluid to carry digestive products to villi

Peptidases

Enzymes that break dipeptides into amino acids

Sucrase, maltase, lactase

Enzymes that break down disaccharides into monosaccharides

Lactose intolerance

Caused by deficiency in lactase, leading to gas and diarrhea

Intestinal lipase

Enzyme that breaks triglycerides into fatty acids and glycerol

Enterokinase

Activates trypsinogen into trypsin for protein digestion

Monosaccharide absorption

Absorbed via active transport or facilitated diffusion into blood capillaries

Amino acid absorption

Absorbed via active transport into blood capillaries

Fat absorption

Fats are absorbed into epithelial cells, reassembled, and transported in chylomicrons

Chylomicrons

Lipid

VLDL

Very low

LDL

Low

HDL

High

Segmentation

Mixing movement of small intestine to increase contact with digestive enzymes

Peristaltic waves

Move contents slowly through small intestine (3–10 hours)

Ileocecal sphincter

Valve between ileum and cecum that controls passage to large intestine

Large intestine

Absorbs water and electrolytes, forms and stores feces

Cecum

Pouch at the beginning of the large intestine that receives chyme from ileum

Colon

Major part of large intestine; includes ascending, transverse, descending, and sigmoid sections

Rectum

Stores feces before elimination

Anal canal

Last part of large intestine, opens to the anus

Internal anal sphincter

Involuntary muscle controlling initial defecation urge

External anal sphincter

Voluntary muscle that allows conscious control of defecation

Intestinal microbiota

Bacteria in the large intestine that synthesize vitamins and process waste

Vitamin K

Produced by intestinal flora, essential for blood clotting

Feces

Composed of undigested food, water, electrolytes, mucus, cells, and bacteria

Brown color of feces

Caused by breakdown of bilirubin and biliverdin by bacteria

Macronutrients

Nutrients needed in large amounts: carbohydrates, lipids, proteins

Micronutrients

Nutrients needed in small amounts: vitamins and minerals

Essential nutrients

Nutrients the body cannot make and must get from diet

Basal Metabolic Rate (BMR)

Rate at which body uses energy at rest

Malnutrition

Poor nutrition due to lack or improper use of nutrients

Undernutrition

Not enough nutrients consumed

Overnutrition

Excess intake of calories with insufficient nutrients