Transcript Digestion 2 - TASIS IB Biology

Welcome to Topic 6: Basic Human Physiology!
Plan for this week!
• Complete 6.1 – digestion – Monday – Thursday
• Wednesday – help lab on DCP and CE (on
demand)
• Friday – LAB – dissetion and food pathology/
identification tests
• Friday – FINAL DESIGN SUBMISSION IS DUE
• MONDAY - DCP and CE due
Topic 6.1: The Digestive System (3 h)
6.1.1 Explain why digestion of large food molecules is essential.
6.1.2 Explain the need for enzymes in digestion.
6.1.3 State the source, substrate, products and optimum pH conditions for
one amylase, one protease and one lipase.
6.1.4 Draw and label a diagram of the digestive system.
6.1.5 Outline the function of the stomach, small intestine and large
intestine.
6.1.6 Distinguish between absorption and assimilation.
6.1.7 Explain how the structure of the villus is related to its role in
absorption and transport of the products of digestion.
So….draw a digestive system!
6.1.4 Draw and label a diagram of the
human digestive system.
You have 2 minutes….
The Components of the Digestive System
Figure 24.1
Simple digestion: Intracellular food processing
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Paramecium
Food is ingested through
endocytosis and forms
food vacuole
Food vacuole fuses with
lysosome,which contains
digestive juices
Nutrients absorbed
through membrane
Vacuole refuses with
membrane and waste is
eliminated through
exocytosis
Simple digestive systems: Extracellular food
processing
•
Food breakdown and
absorption occur in
compartments that are
continuous with outside of
organism
• Gastrovascular cavity:
•
food enters + waste exits
through a single opening
Cnidarians (ex. Hydra) have
this
Functions of the digestive system
• ingestion
• mechanical digestion (processing) (e.g.chewing)
• chemical digestion (enzymatic hydrolysis)
• Secretion
• absorption
• excretion/ elimination of waste products
The Structure of the Digestive Tract
Figure 24.3
How does food move along the digestive tract?
Smooth muscle shows rhythmic cycles of activity
Peristalsis : waves that move a bolus (ball of
food)
Segmentation
Churn (mixing) and fragment a bolus
Let’s watch!
Peristalsis in action...
Peristalsis
Figure 24.4
Digestion is achieved through both chemical and
mechanical breakdown
6.1.1 Explain why digestion of large food
molecules is essential.
6.1.2 Explain the need for enzymes in
digestion.
6.1.3 State the source, substrate, products and
optimum pH conditions for one amylase, one
protease and one lipase.
Why do we need enzymes for digestion?
• Stephen Taylor intro to digestion/enzymes
• zoom into amylase...
Why do we need enzymes for digestion?
Step by step through the digestive tract
• explore the digestive tract
• UPenn animation
• animation of organs of
digestion
Oral (buccal) cavity/pharynx
Its functions include:
• analysis of material before swallowing (touch,
temperature, and taste receptors in tongue)
• mechanical processing by the teeth and tongue
• lubrication
• limited digestion (salivary amylase)
• Production of a food bolus for transportation
to the stomach (via oesophagus) by peristalsis
• The pharynx provides a common pathway for
air, food and liquids
The pharynx
6.1.5 Outline the function of the stomach
• yum!....digestion from the inside
• Storage of undigested food
• Hydrochloric acid lowers pH to 2,
killing bacteria and denaturing
proteins
• Mechanical breakdown of food
through muscular action
• Chemical breakdown of food with
acids and enzymes
(pepsin begins protein digestion)
• Produces chyme
Structure of the stomach
Rugae: rough ridges which allow grinding of food
(mechanical digestion)
Digestion and absorption in the stomach
very little absorption of
nutrients
Control of enzyme (pepsin),
acid (HCl) and hormone
(gastrin) secretion is
controlled by:
1. Cephalic
2. Gastric
3. Intestinal
factors
Control of gastric function
The Stomach
Figure 24.12b
The Stomach Lining
Figure 24.13c, d
6.1.5 Outline the function of the small intestine.
• Important digestive and
absorptive functions
•
pancreas, liver & gall bladder
secrete enzymes and juices
into small intestine
• Small intestine divided into
three sections:
• Duodenum
• Jejunum
• Ileum
Regions of the Small Intestine
Figure 24.16a
Small intestine
Adaptations to increase
surface area for
absorption…
• Plicae (folds)
• Villi (fingerlike
projections)
• Microvilli
Zooming in on the
small intestine
The Intestinal Wall
Figure 24.17b, c
The Intestinal Wall
Figure 24.17d, e
Microvillae
Microvilli (MV) are minute finger
like projections of the luminal (L)
plasma membrane and serve the
purpose of significantly increasing
surface area (as much as 30-fold)
in regions specialized for
absorption, such as here in the
small intestine.
Small Intestine
• Duodenal glands
• produce mucus
• Ileum
• lymph glands (Peyer’s patches)
Functions of the large intestine
• Reabsorbs water and compact material into feces
• Absorb vitamins produced by bacteria
• Store faecal matter prior to defecation
The Large Intestine
The Pancreas
The pancreas and gland cells of the
small intestine secrete digestive
enzymes that chemically break
down complex food molecules into
simpler ones.
These enzymes include trypsin (for
protein digestion), amylase (for
carbohydrate digestion), and lipase
(for lipid digestion).
Figure 24.18a-c
The pancreas
• Pancreatic duct penetrates duodenal wall
• Endocrine functions (hormones)
• Insulin and glucagons
• Exocrine functions (digestive enzymes)
• Pancreatic juice containing many enzymes are
secreted into small intestine
The liver
• Performs regulation of metabolism and blood
and produces bile
• The liver has many different functions
The Gallbladder
Bile liquid is created in the
liver and stored in the
gallbladder. Bile emulsifies
(breaks into small particles)
lipids (fats), which aids in
the mechanical digestion of
fats.
The gallbladder
• Hollow, pear-shaped
organ
• Stores bile
• Helps in digestion of
fats
PLAY
Animation: Accessory Organ