Lecture Exam #2 review

Liver

The largest gland in the body,

located under the diaphragm in the upper right quadrant,

responsible for producing bile and performing numerous metabolic functions

Hepatocytes

The primary functional cells of the liver that process nutrients, store fat-soluble vitamins, and detoxify the blood

Bile

A yellow-green alkaline solution produced by the liver containing bile salts, pigments, cholesterol, and electrolytes

Bile Salts

Cholesterol derivatives in bile that function to emulsify fats, breaking them into smaller droplets for easier digestion

Bilirubin

The chief bile pigment, a waste product of heme, which is converted by bacteria in the small intestine to stercobilin, giving feces its brown color

Hepatic Portal Vein

The vessel that carries nutrient-rich, deoxygenated blood from the digestive organs directly to the liver

Gallbladder

A thin-walled muscular sac that stores and concentrates bile until it is needed in the small intestine

Cholecystokinin (CCK)

An intestinal hormone released in response to proteins and fats that triggers gallbladder contraction and pancreatic juice secretion

Pancreatic Juice

An alkaline mixture of water, enzymes, and electrolytes (mainly bicarbonate) that neutralizes acidic chyme and digests all food categories

Small Intestine

The body's major digestive organ, where almost all nutrient absorption and the completion of chemical digestion occur

Duodenum

The first 10 inches of the small intestine where bile and pancreatic juice enter through the hepatopancreatic ampulla

Jejunum

(B) The middle section of the small intestine (approx. 8 feet long) where the majority of nutrient absorption takes place

Ileum

(C) The final 12-foot section of the small intestine that joins the large intestine at the ileocecal valve

Villi

Fingerlike projections of the intestinal mucosa that increase surface area and contain blood capillaries and lymphatic lacteals

Microvilli

Tiny projections of the plasma membrane on absorptive cells that form the "brush border" and contain digestive enzymes

Intestinal Juice

A watery, slightly alkaline secretion produced by the intestinal glands that helps facilitate the transport and absorption of nutrients

Segmentation

Localized rhythmic constrictions of the small intestine that mix food with digestive juices and increase the rate of absorption

Peristalsis

Rhythmic, wave-like contractions of smooth muscle that move food and waste through the gastrointestinal tract

Salivary Amylase

An enzyme in the mouth that initiates the chemical breakdown of starches into smaller sugars

Pepsin

A stomach enzyme that begins the chemical digestion of proteins into smaller peptide chains

Pancreatic Lipase

The primary enzyme responsible for breaking down triglycerides into fatty acids and monoglycerides in the small intestine

Micelles

Spherical complexes of bile salts and fatty acids that transport lipids to the intestinal surface for absorption

Chylomicrons

Lipoprotein particles formed in intestinal cells that transport absorbed fats into the lymphatic system via lacteals

Large Intestine

The final segment of the GI tract, primarily involved in water and electrolyte absorption and the elimination of feces

Cecum

The blind-ended pouch that marks the beginning of the large intestine, located just below the ileocecal valve

Appendix

A small, finger-like projection of the cecum containing lymphoid tissue and acting as a bacterial storehouse

Colon

The main portion of the large intestine, divided into ascending, transverse, descending, and sigmoid regions

Haustra

Small, pocket-like sacs in the wall of the large intestine created by the muscle tone of the teniae coli

Bacterial Flora

Microorganisms in the large intestine that ferment indigestible carbohydrates and synthesize B complex vitamins and vitamin K

Defecation Reflex

A parasympathetic reflex stimulated by rectal stretching that causes the internal anal sphincter to relax and the rectal wall to contract

Mastication

The mechanical process of chewing where the cheeks and lips hold food between the teeth and the tongue compacts it

Saliva

A fluid that cleanses the mouth, moistens food for bolus formation, and contains enzymes to begin starch digestion

Bolus

A compact mass of food formed by the tongue and moistened by saliva to facilitate swallowing

Deglutition

The medical term for swallowing, which involves both voluntary and involuntary phases

Buccal Phase

The first, voluntary phase of swallowing where the tongue pushes the food bolus into the oropharynx

Pharyngeal-esophageal Phase

The involuntary phase of swallowing controlled by the brain stem, forcing food through the pharynx and into the esophagus

Soft Palate and Uvula

Structures that rise during swallowing to close off the nasopharynx and prevent food from entering the nasal cavity

Epiglottis

A flap of cartilage that blocks the trachea during swallowing to ensure food enters the esophagus

Upper Esophageal Sphincter

A muscular valve that relaxes to allow the food bolus to enter the esophagus from the pharynx

Esophagus

A muscular tube that acts as a "food chute," using peristaltic waves and mucus lubrication to move the bolus to the stomach

Pancreatic Amylase

A pancreatic enzyme released into the small intestine that continues the digestion of starches

Sucrase

A brush border enzyme that breaks down sucrose into glucose and fructose

Lactase

A brush border enzyme that breaks down lactose into glucose and galactose

Maltase

A brush border enzyme that splits maltose into two glucose molecules

Migrating Motility Complex (MMC)

A form of peristalsis that occurs between meals to push remaining chyme and debris forward through the small intestine

Gingivitis

Inflammation of the gums, which if chronic, can lead to bacteria entering the bloodstream

Plicae Circulares

Permanent circular folds of the intestinal mucosa and submucosa that force chyme to spiral, slowing its movement and increasing absorption time

Nutrient

substance in food needed for growth, maintenance, and repair

Macronutrients

three categories of nutrients making up most of the diet: carbohydrates, lipids, and proteins

Micronutrients

vitamins and minerals, required in small but essential amounts

Metabolic fuel

primary use for most nutrients, though some are for building molecules and cells

Water

essential substance accounting for about 60% of food volume

Essential nutrients

molecules the body cannot synthesize in adequate amounts and must be provided by the diet

Nonessential nutrients

hundreds of molecules the body can synthesize, often by liver interconversions

Kilocalories (kcal)

unit measuring nutrient energy; the heat needed to raise the temperature of 1 kg of water by 1°C

Carbohydrate and Protein Energy Value

4 kcal per gram

Lipid Energy Value

9 kcal per gram

USDA MyPlate

guidelines for food portions: fruits, vegetables, grains, protein, and dairy

Basic Dietary Principles

eat only what you need; eat plenty of fruits, vegetables, and whole grains; avoid junk food

Carbohydrate Dietary Sources

mostly plants; lactose in milk; small amounts of glycogen in meat

Sugars

monosaccharides and disaccharides found in fruits, sugarcane, honey, and milk

Starch

polysaccharide found in grains and vegetables

Insoluble fiber

cellulose in vegetables that provides roughage to increase stool bulk and facilitate defecation

Soluble fiber

pectin in apples and citrus that helps reduce blood cholesterol levels

Glucose

the primary carbohydrate molecule used by cells to produce ATP

Fructose and Galactose

sugars converted to glucose by the liver before entering circulation

Neurons and RBCs

cells that rely almost entirely on glucose and die quickly without it

Glycogen or Fat

forms in which excess glucose is stored

Pentose sugars

carbohydrates used for building nucleic acids

Glycocalyx

cellular structure built using short-chain sugars

Carbohydrate Dietary Requirements

45-65% of total daily calories, ideally from complex carbohydrates

Carbohydrate Excess Problems

obesity, diabetes mellitus, dental caries, elevated triglycerides

Carbohydrate Deficit Problems

tissue wasting, metabolic acidosis from accelerated fat use

Lipid Dietary Sources

primarily triglycerides

saturated fats in meat/dairy

unsaturated in seeds/nuts

trans fats in hydrogenated oils

Cholesterol Sources

egg yolks, meats, organ meats, shellfish, and milk products

Liver Cholesterol Production

the liver produces about 85% of blood cholesterol regardless of intake

Essential Fatty Acids

linoleic acid (omega-6) and linolenic acid (omega-3), which the liver cannot make

Adipose Tissue

provides protective cushioning, insulation, and energy storage

Myelin Sheaths

neuronal structures largely composed of phospholipids

Cholesterol Functions

stabilizes cell membranes; precursor for bile salts and steroid hormones

Prostaglandins

regulatory molecules made from linoleic acid involved in BP regulation and inflammation

Lipid Dietary Requirements

20-35% of total caloric intake; saturated fats limited to 10% or less

Lipid Excess Problems

obesity; increased risk of cardiovascular disease

Lipid Deficit Problems

weight loss; heat loss control issues; poor growth; skin lesions; depression

Complete Proteins

animal products and soybeans that meet all essential amino acid requirements

Incomplete Proteins

legumes, nuts, and grains LOW in one or more essential amino acids

All-or-None Rule

all amino acids needed for a specific protein must be present simultaneously or the protein cannot be built

Caloric Adequacy

if carbohydrate or fat intake is insufficient, body proteins will be burned for energy instead

Anabolic Hormones

GH and sex hormones that promote protein synthesis

Glucocorticoids

hormones that promote protein breakdown and conversion of amino acids to glucose

Positive Nitrogen Balance

synthesis exceeds breakdown; occurs during growth, pregnancy, and tissue repair

Negative Nitrogen Balance

breakdown exceeds synthesis; occurs during stress, infection, or starvation

Protein Dietary Requirement

0.8 g per kilogram of body weight daily

Protein Deficit Problems

profound weight loss; edema due to low plasma proteins; miscarriage or premature birth

Vitamins

organic compounds acting as coenzymes; needed in minute amounts for macronutrient use

Vitamin D

vitamin synthesized in the skin

Vitamins B and K

vitamins synthesized by intestinal bacteria

Beta-carotene

a provitamin found in carrots that the body converts to Vitamin A

Water-soluble Vitamins

B complex and C; absorbed with water; not stored in the body

Fat-soluble Vitamins

A, D, E, and K; absorbed with lipids; stored in body fat (except Vitamin K)