Post on 28-Dec-2015
Digestion, Absorption, Digestion, Absorption, and Transportand Transport
Overview Digestive SystemOverview Digestive System
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. Mechanical
2. Enzymatic (chemical)
Overview Digestive SystemOverview 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)
GI Tract GI Tract AnatomyAnatomy
Digestive TractDigestive Tract
Layers of GI tract organsLayers of GI tract organs Serosa (outermost)Serosa (outermost)
• Interface between GI tract and lymph & blood Interface between GI tract and lymph & blood Muscle LayersMuscle Layers
• Longitudinal musclesLongitudinal muscles• Circular musclesCircular muscles
Submucosal and Mucosal and layers Submucosal and Mucosal and layers (innermost)(innermost)• Nerves, blood and lymph vessels Nerves, blood and lymph vessels • Cells of the mucosal layer produce secretionsCells of the mucosal layer produce secretions
MouthMouth
Structure – Structure – teeth, tongue, salivary glandsteeth, tongue, salivary glands SecretionsSecretions
SalivaSaliva Salivary amylase …..Salivary amylase …..
Digestion Digestion Mechanical ….Mechanical …. Enzymatic/chemical ….Enzymatic/chemical ….
Swallow Swallow tongue pushes food tongue pushes food pharynx pharynx …… ……
EsophagusEsophagus
Structure – 12” tubeStructure – 12” tube UES and LESUES and LES
FunctionFunction Transports food from mouth to stomachTransports food from mouth to stomach Peristalsis and gravity aid food movement Peristalsis and gravity aid food movement
Secretions -- mucusSecretions -- mucus Digestion Digestion
Mechanical (limited)Mechanical (limited) Enzymatic/chemical – starch digestion continuesEnzymatic/chemical – starch digestion continues
StomachStomach Structure – Structure –
muscular sack muscular sack that can expandthat can expand extra muscle extra muscle
layer to aid in layer to aid in the mechanical the mechanical digestion of digestion of food (pg 73)food (pg 73)
StomachStomach
Stomach Related SecretionsStomach Related Secretions
1. Gastrin – hormone that stimulates stomach to release secretions
2. Hydrochloric Acid (HCl) -- unravels proteins, kills bacteria, activates pepsinogen
3. Pepsinogen – once activated, begins protein digestion
4. Mucus – secreted by goblet cells, protects stomach, moistens food
Stomach - - Digestion
Mechanical• Stomach muscles grind food into a paste called
chyme
Enzymatic/chemical• Proteins uncoiled• Protein digestion to polypeptides begins• Starch digestion stops
Small IntestineSmall Intestine
Small Intestine (SI)Small Intestine (SI)
Function – The SI is where:1. the majority of digestion to absorbable units
occurs• Digestion of carbohydrates, fats, and proteins • Vitamins and minerals do not need digestion
2. Nutrients are absorbed into either capillaries or lacteals
Small IntestineSmall Intestine
The Small Intestinal VilliThe Small Intestinal Villi
The Small Intestinal VilliThe Small Intestinal Villi
Small IntestineSmall Intestine
Digestion - MechanicalDigestion - Mechanical Peristalsis pushes food through SIPeristalsis pushes food through SI Segmentation mixes chyme with digestive Segmentation mixes chyme with digestive
enzymes enzymes • Also breaks up food mass into smaller massesAlso breaks up food mass into smaller masses
Bile emulsifies fatsBile emulsifies fats
Peristalsis & SegmentationPeristalsis & Segmentation
Muscular Action Muscular Action of Digestionof Digestion
SegmentationSegmentation
SISI
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 to liver
Preparing Nutrients for Preparing Nutrients for TransportTransport
Transport pathways Bloodstream
Water-soluble nutrients and smaller products of fat digestion
Liver Lymphatic system
Larger fats and fat-soluble vitaminsChylomicronsBypass liver at first
The Vascular SystemThe Vascular System
Closed system of vessels Heart pump
Blood Delivers oxygen and nutrients Removes carbon dioxide and wastes Blood flow
Special routing for digestive system Liver
The Vascular SystemThe Vascular System
Large Intestine or ColonLarge Intestine or Colon
Large Intestine or ColonLarge Intestine or Colon
Undigested foods (fiber) enter into colonUndigested foods (fiber) enter into colon Unabsorbed nutrients pass into colonUnabsorbed nutrients pass into colon
E.g. calcium, iron, cholesterol trapped in fiberE.g. calcium, iron, cholesterol trapped in fiber
ColonColon
StructureStructure 5-6’ long5-6’ long Wider diameter than SIWider diameter than SI
• No villi or microvilliNo villi or microvilli Appendix is a little pouch near beginning of Appendix is a little pouch near beginning of
colon colon Colon “wraps around” SIColon “wraps around” SI
Large Intestine or ColonLarge Intestine or Colon