Transcript Human Biology

Anatomy and Physiology
Chapter 23 – Digestive System
Digestive System - Anatomy
 Digestive
System vs. Digestive or
Gastrointestinal (GI) Tract
 What elements make up the GI tract?
 Demo
 What
additional elements are there?
 Teeth,
tongue, gallbladder, liver, pancreas,
and salivary glands
Digestive System
Overview – the digestive tract
can be seen as a “disassembly line”
 Physiology
 Ingestion
 Propulsion
 Figure
– this occurs by peristalsis
23.3 and CD Animation
Digestive System
 Physiology
Overview
digestion – this physically
prepares food for chemical digestion
 Chemical digestion – breaks large molecules
into small molecules
 Absorption
 Defication
 Mechanical
 Figure
23.2
Digestive System - Anatomy
 Histology
– Figure 23.6
Digestive Tract
 The
mouth:
 Salivary
glands are stimulated by food
entering the mouth or even by seeing,
smelling, or thinking about food
 Saliva is composed of:
Water
(97-99.5%)
salivary amylase
Lysozyme and IgA antibodies
 Figure
23.9
Digestive Tract
 Teeth
– Figures 23.10 and 23.11
Digestive Tract
 Cavity
formation - Figure from other text
Digestive Tract (cont.)
 Pharynx
 Esophagus
 Heart
burn – Figure 23.1
Digestive Tract (cont.)
 Stomach
– the temporary “storage tank”
 Stomach
size and amazing rugae!
 The mucosa of the stomach contains gastric
glands that produce mucus & gastric juice:
Pepsin
- protein digesting enzyme
Hydrochloric Acid (HCl) – function?
 Gastric
ulcers and Helicobacter pylori
 Tagamet
 Figures
and Zantac are proton-pump blockers
23.14 and 23.15
Anatomy of the Digestive Tract (cont.)
 The
stomach mixes food with stomach juices
 This
 Some
produces chyme
lipid-soluble substances (like alcohol)
are absorbed in the stomach, but most food is
not
 Food leaves the stomach in 2-4 hours
 CD Animation
 Vomiting
 Stomach by-pass surgery – Figure 23.14
Anatomy of the Digestive Tract (cont.)
 Small
Intestine (or should it be called the
“long intestine”?)
 Major
site of digestion and absorption of food
 As food enters the small intestine from the
stomach, it is mixed with:
bile
(from the liver) - emulsifies fat
pancreatic juice - contains digestive enzymes
and sodium bicarbonate
 Figure
23.20
Anatomy of the Digestive Tract (cont.)
 The
surface area of the small intestine is roughly
equal to the size of a tennis court!!!
 How is that possible?
Circular
folds
Villi – finger-like projections of the mucosa
Microvilli – what are these?
Figure 23.21
Anatomy of the Digestive Tract (cont.)
 Water
soluble nutrients enter the blood
stream
 Lipid soluble nutrients enter lacteals
 Any material that is not digested and
absorbed moves on to the large intestine.
Figure
23.21
Anatomy of the Digestive Tract (cont.)
 Large
Intestine
 absorbs
water, salts, minerals and some
vitamins
 ~500
ml of chyme enter each day, but only 150
ml of feces is produced
 stores
undigested material until it is
eliminated
 Appendicitis – Figure 23.29
Anatomy of the Digestive Tract (cont.)
 Polyps
and colon cancer
fat
consumption increases likelihood
fiber decreases likelihood
 Flatus
 Rectum
and Anus - function to eliminate
undigested material (feces)
 3/4
water, 1/4 solid material
 Solid material is largely bacteria from the large
intestine
Over
1 billion bacteria in one gram of feces
Accessory Organs
 Liver
- largest organ in the body
 Microscopic anatomy:
arteries – oxygen rich blood
Hepatic portal veins – these carry blood from
the GI tract
Hepatic ducts – bile
Central vein  inferior vena cava
Hepatic
 Figure
23.24
Accessory Organs (cont.)
 Liver
Functions:
 Bile
production
 Storage (usually short term)
 Carbohydrates
– glycogen
 Fat
– A, B12, D, E, and K
 Copper and iron
 Vitamins
 Nutrient
 Amino
Interconversion
acids and glycerol to glucose
 Fatty acids to phospholipids, etc.
Accessory Organs (cont.)
 Detoxification
 The
liver removes toxic substances from the blood
 Alcohol and ammonia
 Phagocytosis
 Synthesis
of Blood Proteins
 Albumin,
fibrinogen, heparin, clotting factors, etc.
 Structure/function
– Figure 23.24
Accessory Organs (cont.)
 Hepatitis
is an infection of the liver
 Cirrhosis – chronic inflammation of the liver
(leads to the replacement of liver cells with
connective tissue)
 Gall Bladder - stores bile
 gall
stones - crystals of cholesterol
 Figure 23.20
Accessory Organs (cont.)
 The
Pancreas
 What
does it do?
 Endocrine
and exocrine functions
 Sodium
Bicarbonate
 Enzymes:
pancreatic
amylase
Trypsin, chymotrypsin
lipase
Nuclease
 Figure
23.20
Hormonal Control of the Digestive
System
 Table
23.1 and Figures 23.16, 23.25, and 23.28
Digestion, Absorption, & Transport
 Chemical
Digestion
 Breaks
macromolecules down into monomers
 Carbohydrates – How are these broken down?
Figure
23.33
Digestion, Absorption, & Transport
 Lactose
intolerance
 Glucose is absorbed via cotransport with Na+
 It then enters into the blood
 Figure from other text
Digestion, Absorption, & Transport
 Proteins
– how are these digested?
 Figures
23.33 and 23.34
Digestion, Absorption, & Transport
are also absorbed by cotransport with Na+
Figure from other text
 Proteins

Digestion, Absorption, & Transport
 Nucleic Acids
absorbed
 Figure 23.33
– DNA and RNA are digested and
Digestion, Absorption, & Transport
– fats, cholesterol, steroids, some
vitamins
 Lipids
 Emulsification
by bile
 Digestion by lipase
 Breaks
 Figures
triglycerides into fatty acids and glycerol
23.33 and 23.35
Digestion, Absorption, & Transport
 The
fatty acids and other lipids then form micelles by
associating with bile salts
 The lipids can then enter the cells by simple diffusion
 Figure from other text
Digestion, Absorption, & Transport
 Once
inside the cells the fatty acids and glycerol are
used to produce triglycerides again
 These
attach to proteins, cholesterol, and phospholipids to
form chylomicrons
 These then leave the cell and enter the lacteals
 Figure
from other text and Figure 23.36
Digestion, Absorption, & Transport
 Chylomicrons
eventually enter into the blood and go to the
adipose tissue and liver
 Low-Density
Lipoprotein (LDL) vs. High-Density
Lipoprotein (HDL)
 VLDL leaves
the liver
 As lipids are removed in adipose tissue VLDLLDL
 LDL then delivers lipids to other body cells
 HDL is a protein which picks up any extra cholesterol and
transports it back to the liver to make bile
 Figure
24.22
Digestion, Absorption, & Transport
 It
is considered healthy to have high HDL and
low LDL. Why?
 What would be the problem with high LDL and
low HDL?
Summary
 Table
23.2
Summary
 CD
animation (Sm. Intestine)