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! 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 Heart and blood vessels  Lympahtic system Lympahtic vessels and lymph nodes Lympahtic vessels and lymph nodes

Blood  Blood is made of:  Plasma – fluid portion of blood  Water soluble nutrients are dissolved in the plasma  Red blood cells  White blood cells  Platelets  Proteins and other substances  Fat soluble nutrients are often carried by water soluble proteins

CV System – more detail than we have time for  Heart  -> Lungs Veins bring deoxygenated blood to the right side of the heart Veins bring deoxygenated blood to the right side of the heart Right side of the heart pumps deoxygenated blood to the lungs Right side of the heart pumps deoxygenated blood to the lungs Blood returns to the left side of the heart oxygenated Blood returns to the left side of the heart oxygenated Left side of heart pumps blood to entire body by way of arteries Left side of heart pumps blood to entire body by way of arteries

Blood Vessels  Blood leaves heart through an artery (aorta)  Vessels branch in to smaller and smaller vessels  Smallest blood vessel is the capillary  Exchanges of gases, nutrients and wastes between body cells and the CV system occur at the capillary level

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

Lymphatic System  Lymph vessels transports: white blood cells white blood cells excess fluid between cells excess fluid between cells Returns the fluid to the bloodReturns the fluid to the blood fat soluble nutrients absorbed from the SI fat soluble nutrients absorbed from the SI  Lymph vessels branch to form lacteals Fat soluble nutrients are absorbed in to lacteals – page 91 Fat soluble nutrients are absorbed in to lacteals – page 91

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 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 target cells Cells with receptors for the hormone Cells with receptors for the hormone  Binding triggers a change in the target cells/organ See table 3-2 on page 93 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: 1. 1.Mechanical 2. 2.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 Continuous tube from mouth to anus See board and page 97See board and page 97

GI Tract Anatomy

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

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

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

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

Stomach  Structure – muscular sack that can expand extra muscle layer to aid in the mechanical digestion of food (pg 101) 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 pepsinogen Pepsinogen – once activated, begins protein digestion

Stomach Related Secretions Mucus – secreted by goblet cells, protects stomach, moistens food Intrinsic factor (IF) – IF binds vitamin B-12 Required for B-12 to be absorbed

Stomach related secretions Function Gastrin HCl Pepsinogen Mucus Intrinsic Factor

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

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  Length – 10 feet (~ 21’-22’ long when relaxed) Layers ….. Layers ….. Mucosal folds, villi, microvilli …. Mucosal folds, villi, microvilli …. Goblet cells and crypts – create secretions Goblet cells and crypts – create secretions Lacteals and capillaries …. Lacteals and capillaries ….  Sections DuodenumDuodenum JejunumJejunum IleumIleum

Small Intestine

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

Small Intestine  Secretions of the SI, cont’d Hormones Hormones Secretin …Secretin … CCK ….CCK …. Gastric-inhibitory peptide …Gastric-inhibitory peptide …

Small Intestine - Hormones   Secretin – produced when chyme enters SI stimulates pancreatic secretions   *CCK – produced when fat enters SI Stimulates _________to release ______ Slows GI motility (slows peristalsis) **Cholecystokinin   Gastric–inhibitory peptide – produced when chyme enters SI Slows stomach secretions Slows GI motility

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

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

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

Secretions into SISecreted by and Function Sodium bicarbonate Digestive Enzymes Bile

Small Intestine  Digestion - Mechanical Peristalsis pushes food through SI Peristalsis pushes food through SI Segmentation mixes chyme with digestive enzymes Segmentation mixes chyme with digestive enzymes Also breaks up food mass into smaller massesAlso breaks up food mass into smaller masses Bile emulsifies fats Bile emulsifies fats

Peristalsis & Segmentation

Muscular Action of Digestion Segmentation

SI - Digestion  Mechanical digestion Muscle action breaks food into smaller and smaller pieces Muscle action breaks food into smaller and smaller pieces Bile emulsifies fats Bile emulsifies fats  Chemical/Enzymatic Pancreatic and SI enzymes digest carbs, fats, and proteins to absorbable units Pancreatic and SI enzymes digest carbs, fats, and proteins to absorbable units

SI - Absorption  Absorbed into capillaries (blood) Digested carbohydrates and proteins Digested carbohydrates and proteins Minerals Minerals Some require helper proteins/cells on walls of SI to be absorbedSome require helper proteins/cells on walls of SI to be absorbed Water soluble vitamins 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

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

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

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

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

Colon  Absorption Water, salts, vitamins made by bacteria are absorbed into __________ (answer is either capillaries or lacteals. Which one is it?..you know!) 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 little fiber in diet  Too much 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 2 anal sphincters Internal and external anal sphinctersInternal and external anal sphincters