BIOS 1310 lab quiz #8

5 Processes of the digestive system

ingestion

digestion

absorption

compaction

defecation

Ingestions

voluntary intake of food into the oral(buccal) cavity

mechanical and chem digestion

Mechanical digestion

increases number of food particles —→ increases exposed surface area

allows for maximum exposure to and mixing w digestive enzymes

chemical digestion

breaks down complex macromolecules into fundamental building blocks through enzymatic action

mastication

chewing

initiates mechanical digestion in mouth

salivary glands

parotid

sublingual

submandibular

produce saliva

saliva

fluid substance loaded w digestive enzymes for chem digestion of a meal

salivary amylase

begins breakdown of starch into simpler carbohydrates

lingual lipase

contributes to early digestion of lipids

deglutition

swallowing

oral cavity —→pharynx—→esophagus

marks transition from voluntary to involuntary control of digestion

Peristalsis

series of coordinated wave-like contractions of smooth muscle

ensure forward propulsion of bolus

Stomach

both mechanical and chem digestion

mix and grind bolus —→chyme

• churing and retropulsion

  • repeatedly forces chyme against pyloric sphincter

    • reduces particle size

    • ensures thorough mixing and gastric secretions

Parietal cells and chief cells play a role in the chem digestion

carbohydrate digestion is mostly halted due to acidic conditions

Parietal cells

secrete HCl

• creates hgihly acidic environment

  • denatures proteins

  • destroys any accidentally ingested pathogens

  • activates digestive enzymes

produce intrinsic factor

Chief cells

release pepsinogen

• inactive precursor of pepsin

  • activates in presence of HCl

Pepsin

begins breakdown of proteins into smaller peptides

Intrinsic factor

essential for absorption of vitamin B12 in distal ileum

from the stomach chyme moves to…

the small intestine

• where majority of digestion and nearly all nutrient absorption occur

In duodenum, chyme is…

mixed w secretions from pancreas and bile from liver and gallbladder

Pancreas

produces

• pancreatic amylase

  • carbohydrates

• pancreatic lipase

  • lipids

• several zymogens

Zymogens

precursor protease enzymes for proteins

activated within small intenstine

trypsinogen converts to…

trypsin by enterokinase

trypsin

activates other proteases

allows for efficient protein digestion

bile

produced in liver and stored in gallbladder

aids in digestion of lipids by emulsifying large fat globules into smaller droplets

• increases surface area available for enzymatic action

Segmentation

mechanical digestion in sm intestine

process involving localized contractions that mix chyme w digestive secretions and enhance contact w intestial mucosa

Inner, mucosal surface of sm intestine

highly specialized for absorption

lined w enterocytes that possess microvilli

• forms brush boder to capture and process nutrients

Brush border

embedded are enzymes that complete final stages of digestion

break down carbohydrates and peptides into simplest, most absorbable forms

Lacteals

lipids are absorbed by these

Residue

any material that cannot be digested or absorbed

is passed into large intestine to undergo compaction

Compaction

water removal

Biliary tree

aka biliary tract or biliary system

complex branching network of organs and ducts responsible for producing, storing, and transporting bile

vital role in breakdown of fats

pathway for waste removal

delivers bile to sm intestine

located in upper abdomen

center of biliary tree

liver

Liver

produces bile

hepatocytes

• constantly secrete bile into canaliculi

hepatic ducts

r and l

exit liver and join to form common hepatic duct

2 pathways for bile after common hepatic duct

directly toward sm intestine

through cystic duct to the gallbladder

Cholecystokinin

CCK

released when food (fatty) enters sm intestine

stimulates gallbladder to contract and release bile back through the cystic duct and into the common bile duct. CBD joins w pancreatic duct and empty into duodenum through ampulla of vater

Emulsifying of fats

preformed by bile once in the duodenum

breaks large fat globules into smaller droplets

• makes them easier for digestive enzymes to act upon

Bile also…

carries waste products

• bilirubin

• cholesterol

• toxins

from liver to intestines for excretion

Bile acids

reabsorbed in the sm intestine and returned to liver through bloodstream

Common conditions of the biliary system

gallstones

bile duct structures

cancers

lead to symptoms such as

• r upper quadrant pain

• jaundice

• nausea

lipoproteins

specialized particles made of lipids and proteins

• cholesterol

• triglycerides

essential for metabolism

• delivering energy

• supporting hormone production

• maintaining cell membranes

structure determines density

density of lipoproteins

the more protein they contain the denser they are

main types of lipoproteins

chylomicrons

VLDL

LDL

HDL

Chylomicrons

largest and least dense lipoproteins

form in intestines after eating

transport triglycerides to peripheral tissues

• muscles and adipose tissue

where these fats are used for energy or storage

VLDL

very low density lipoproteins

produces by the liver

carry triglycerides synthesized for excess nutrients

main role is to deliver endogenous trriglycerides to adipose tissue for storage

As VLDLs lose triglycerides, they shrink and become denser transitioning to LDL

LDL

low density lipoproteins

primary carriers of cholesterol in the blood

formed after VLDL shed most of their triglycerides (rich in cholesterol)

taken up by cells through receptor mediated endocytosis

• cells use the cholesterol for membrane structure and steroid hormone synthesis

High levels of LDL

excess cholesterol can deposit in artery walls

• forms plaques

• increases risk:

  • atherosclerosis

  • heart attack

  • stroke

LDL is labeled…

bad cholesterol

HDL

High density lipoproteins

serve a protective opposite role

produced in the liver as small, protein rich particles

circulates through bloodstream collecting excess cholesterol and phospholipids from tissues

returns cholesterol to liver where it is excreted in bile or converted into bile acids

• reverse cholesterol transport

  • helps reduce cardiovascular risk

“good cholesterol”

Cholesterol levels

200 mg/dL

• desirable

Most cholesterol in the body is produced…

internally by the liver

body adjusts its own production based on dietary intake

dietary cholesterol alone has less impact on blood cholesterol levels

SFAs

Saturated fatty acids

play more significat role in raising cholesterol levels

certain SFAs increase serum cholesterol by reducing its uptake into tissues

Unsaturated fats

help lower cholesterol

Exercise

lowers blood lipid levels through multistep process

• increases breakdown of triglycerides in adipose tissue

• shrinks VLDL particles

• promotes transder of cholesterol to HDL for removal by liver

imporvies overall HDL to LDL ratio

2 categories of nutrients

macronutrients

micronutrients

together they support everything form energy production and metabolism to immune function and long-term disease prevention

macronutrients

required in large amounts to provide energy

form the foundation of daily energy intake

Carbohydrates

should make up roughly 45-50% of daily calories

serve as body’s primary energy source

when consumed they are broken down into glucose

• fuels cells and supports brain and muscle function

Complex carbohydrates

whole grains

fruit

veggies

provide fiber

promote more stable blood glucose levels

fiber

nondigestible form of carbohydrate

plays additional role in:

• digestive health

• satiety

• cholesterol reduction

Proteins

account for 10-35% of faily caloric intake

critical for structural and functional roles

composed of AAs that body uses to:

• build and repair tissues

• synthesize enzymes and hormones

• support immune functions

Current recommened intake of protein

0.8 g per kg of body weight

minimum requirement

Higher intake of protein

better supports muscle maintenance

Lipid

should comprise about 20-35% of daily calories

most energy dense macronutrient

provides energy

essential for mainting cell membrane structure

producing hormones

insulating the body

protects vital organs

enable absorption of fatsoluble vitamins

• a,d,e,k

Unsaturated fats

beneficial outcomes

saturated and trans fats

should be limited due to link to cardiovascular disease

Micronutrients

needed in smaller amounts

maintains normal physiological function

enzyme activity

gene expression

protection against oxidative stress

vitamins

• a,c,d,e,k and B complex gorup

minerals:

• calcium, iron, potassium, magnesium, zinc

Whole foods

legumes, whole grains, fruits, veggies, nuts, lean proteins

associated with lower risks of chronic diseases

Serving size

standardized to allow comparison between similar food

what people typically eat not what they should

Calories (kcal)

indicate how much energy is obtained from one serving of food

What nutrients should be limited and why?

saturated fat, sodium, added sugars

excessive intake is associated w chronic disease

Nutrients that are encourages

bc many people do not consume enough of them

dietary fiber, vitamin D, calcium, iron, potassium

Percent daily value

indicates how much a nutrient in one serving contributes to the total daily recommended intake

5% DV or less

low

20% or more DV

high

Esophagus

Stomach

esophagus

hard palate

laryngopharynx

oral cavity

oropharynx

mandibular teeth

maxillary teeth

tooth numbers

gingiva

mandibular teeth

maxillary teeth

parotid duct

parotid gland

sublingual gland

submandibular duct

submandibular gland

ascending colon

cecum

descending colon

duodenum

falciform ligament

gallbladder

greater omentum

hepatic duct

ileocecal junction