CH 3: The Human Body; A Nutrition Perspective

Chapter Overview This chapter covers everything from cell structure to all of the systems of the body! This is the content of BIO 100 in one chapter! We will focus on the digestive system and systems that directly relate to the function of this system..

Sections Covered While we may touch on content in other sections, we will focus on: Cardiovascular & lymphatic system (3.4) Endocrine system (3.6) Digestive system (3.8)

Cardiovascular & Lymphatic Systems CV and lymphatic system circulate fluids in the body CV system Heart and blood vessels Lympahtic system Lympahtic vessels and lymph nodes

Components of Blood Plasma – fluid portion of blood Red blood cells Water soluble nutrients are dissolved in the plasma Red blood cells White blood cells Platelets Proteins Lipoproteins Fat soluble nutrients attach to water soluble proteins and form lipoproteins

CV System & Digestive Tract, page 90 Water soluble nutrients are absorbed in to capillaries in the small intestine (SI) (6) Capillaries merge to form the portal vein which transports nutrients to the liver (7) CV system then transports nutrients to the cells of the body

Lymphatic System Circulatory system made of lymph vessels and nodes Lymph vessels transport: white blood cells excess fluid between cells fat soluble nutrients absorbed from the SI Fat soluble nutrients are absorbed in to smallest lymph vessels, called lacteals

Lymphatic System Lymph vessels leaving the SI merge with veins near the heart Fat soluble nutrients in the lymph enter the blood, go through the heart and lungs and are then circulated in the blood

Endocrine System Endocrine glands secrete hormones Hormones enter the blood and bind to cells with receptors for the hormone Binding triggers a change in the target cells/organ See table 3-2 on page 93

Endocrine System

Digestive System (finally) Functions: Digestion, Absorption, Elimination Digestion – process of breaking down foods to release nutrients Goal is to break nutrients into absorbable units 2 types of digestions: Mechanical Chemical (enzymatic)

Overview Digestive System Absorption – movement of nutrients out of GI tract into blood or lymph Water soluble nutrients  Fat soluble nutrients  Excretion – elimination of undigested foods (feces)

Overview Digestive System Structure Gastrointestinal (GI) Tract Continuous tube from mouth to anus See board and page 97 Accessory organs - food does not pass through these organs Liver Gall bladder Pancreas

GI Tract Anatomy

Digestive Tract Layers of GI tract organs Serosa (outermost) Interface between GI tract and lymph & blood Muscle Layers Longitudinal muscles Circular muscles Submucosal and Mucosal and layers (innermost) Nerves, blood and lymph vessels Cells of the mucosal layer produce secretions

Mouth Structure – teeth, tongue with taste buds, salivary glands Secretions Mucos Saliva Salivary amylase Digestion Mechanical …. Enzymatic/chemical …. Swallow  tongue pushes food  pharynx  ……

Esophagus Structure – 12” tube with sphincters Function UES and LES Function Transports food from mouth to stomach Peristalsis and gravity aid food movement Secretions -- mucus Digestion Mechanical (limited) Enzymatic/chemical – starch digestion continues

Stomach Structure ….page 101 Secretions ….. Digestion …… Mechanical Enzymatic/chemical

Stomach Structure – muscular sack that can expand extra muscle layer to aid in the mechanical digestion of food (pg 101)

Stomach Related Secretions Gastrin hormone that stimulates stomach to release secretions Hydrochloric Acid (HCl) unravels proteins kills bacteria activates the enzyme pepsinogen Makes minerals soluble Pepsinogen once activated, begins protein digestion

Stomach Related Secretions Mucus secreted by goblet cells protects stomach Moistens/lubricates food mass = chyme Intrinsic factor (IF) Binds vitamin B-12 Required for B-12 to be absorbed in SI

Stomach related secretions Function Gastrin HCl Pepsinogen Mucus Intrinsic Factor

Stomach - Digestion Mechanical Enzymatic/chemical Stomach muscles grind food into a paste called chyme Enzymatic/chemical Proteins uncoiled Protein digestion to polypeptides begins Starch digestion stops (why??)

Chyme leaves the stomach through the _____________ sphincter and enters the small intestines. Small amounts of chime enter SI at a time

Small Intestine (SI) Function – The SI is where: the majority of digestion to absorbable units occurs Digestion of carbohydrates, fats, and proteins Vitamins and minerals do not need digestion Nutrients are absorbed into either capillaries or lacteals

Small Intestine Structure – see page 102 Sections Length – 10 feet (~ 21’-22’ long when relaxed) Layers ….. Mucosal folds, villi, microvilli …. Goblet cells and crypts – create secretions Lacteals and capillaries …. Sections Duodenum Jejunum Ileum

Small Intestine

The Small Intestinal Villi

The Small Intestinal Villi

Small Intestines Secretions of the SI Mucus Secreted by ____________ cells Digestive enzymes that finish the digestion of carbs, fats, and proteins Secreted from crypts

Secretions of the SI, cont’d 3. Hormones Secretin produced when chyme enters SI stimulates pancreatic secretions Gastric-inhibitory peptide Slows stomach secretions Slows GI motility Cholecystokinin - CCK produced when fat enters SI Stimulates _________to release ______ Slows GI motility (slows peristalsis)

Secretions of SI When Secreted and Function Mucus Digestive Enzymes Secretin CCK Gastric inhibitory peptide

Secretions into SI Pancreatic secretions: Released in response to ________ Sodium bicarbonate Neutralizes acidic chime Digestive enzymes that begin the digestion of carbs, fats, and proteins

Secretions into SI Liver and Gall Bladder - Bile Function of bile: Liver makes bile Gall bladder concentrates and stores bile Bile is released into SI in response to the hormone _______ Function of bile:

Secretions into SI Secreted by and Function Sodium bicarbonate Digestive Enzymes Bile

SI - Digestion Mechanical digestion Chemical/Enzymatic Muscle action breaks food into smaller and smaller pieces Peristalsis pushes food through SI Segmentation mixes chyme with digestive enzymes Bile emulsifies fats Chemical/Enzymatic Pancreatic and SI enzymes digest carbs, fats, and proteins to absorbable units

Peristalsis & Segmentation

SI - Absorption Absorbed into capillaries (blood) Digested carbohydrates and proteins Minerals Some require helper proteins/cells on walls of SI to be absorbed Water soluble vitamins Blood takes nutrients to the liver for processing after absorption (pg 90)

SI - Absorption Absorbed into lacteals (lymph) Digested fats Fat soluble vitamins Cholesterol Nutrients travel through lymph system to chest area where lymph and blood join Nutrients enter blood and travel through body

SI Review What is the relationship between the structure of the SI and its function?

Large Intestine or Colon Undigested foods (fiber) enter into colon Unabsorbed nutrients pass into colon E.g. calcium, iron, cholesterol trapped in fiber

Colon Structure Ileocecal sphincter connects colon to SI Appendix is a little pouch near beginning of colon Colon is ~5-6’ long, “wraps around” SI Wider diameter than SI No villi or microvilli No digestive enzymes Pages 104/105

Colon Secretions Mucus Bacteria living in colon Digest small amounts of fiber and undigested nutrients Often produce…...

Colon Absorption Fiber attracts water Water, salts, vitamins made by bacteria are absorbed into __________ (answer is either capillaries or lacteals. Which one is it?..you know!) Fiber attracts water Too little fiber in diet  Too much fiber in diet 

Rectum and Anus Feces pass from colon into rectum Rectum stores feces until excretion occurs Feces exit body via anus 2 anal sphincters Internal and external anal sphincters