3d-Human Digestive System 2009

8/14/2019 3d-Human Digestive System 2009

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Human Digestive

System

Chapter 10.2

Ms. Ho


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Ingestion

Digestion Absorption

Excretion

Functions of the Digestive

System

*Note: alternate terms for the Digestive Tract are GI

(gastrointestinal) Tract & Alimentary Canal


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Mouth and Oral Cavity

Mouth opens to the

Oral Cavity

Teeth

Salivary Glands

Tongue

Other Structures:

uvula, soft palate,

hard palate, tonsils


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Teeth Structure & Function

Mechanical digestion

OR breakdown of food

Incisors: bite & cut

Canines: tearing &

shreading

Bicuspids/Premolars:

pierce & tear Molars: crush & grind


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How are teeth modified in

organisms?

Carnivore Herbivore Omnivore


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Salivary Glands

Food is mixed with saliva that is produced by

3 pairs of salivary glands

Parotid (largest)

Sublingual (smallest)

Submandibular

Uses ducts (tubular

canals) to transportsecretions to mouth


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Saliva

Presence of food triggers nervous reflex insalivary glands release saliva via ducts

Saliva is 99% water, mucus (glycoprotein)& enzymes (i.e. salivary amylase)

Function:

protects lining of oral cavity from abrasion &lubricates food for easier swallowing

chemical digestion: amylase breaks downpolysaccharide (amylose maltose)


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Functions of the Tongue

Helps mix saliva &food together

Positions food on

molars for chewing Moves food around

until it forms a bolus(food ball) & pushes

it back to pharynx Primary organ for

taste


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Tongue & Taste Buds

Muscle containing

papillae pimple-like

structure on upper

surface of tongue thathouses the taste buds

4 sensory tastes:

Sweet

Salty Sour

Bitter


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Location of Taste Buds

Q: Are you a

Super-taster?


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Other Oral Cavity structures

Uvula: flap of tissue covering nasal cavity

when swallowing food

Tonsils: lymphoid tissue on either side of

uvula in back of throat that produces

antibodies

Hard Palate: roof of mouth, hard ridges

Soft Palate: further back in mouth endingin the uvula


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Pharynx Common passageway for

food, liquids, and air

Pharynx muscles assist in

swallowing of bolus

Region connecting oralcavity & pharynx is the

Oropharynx

Epiglottis: flap of tissue

that covers over openingof trachea (glottis)

prevents food from

entering airway


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Swallowing

Food

Trachea moves up

against epiglottis to

close the opening

& prevent food from

entering the trachea

Mucin is secretedby back of throat &

esophagus wall


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Structure of the Esophagus

Muscular, flexible

tube, ~25cm long

3 layers:

Mucosa (inner): lining

covered in mucus

Submucosa (middle):

nerves, blood & lymph

vesselsMuscularis (outer):

circular & longitudinal

muscle


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Function of the Esophagus

Cross-sectional

View

To conduct food from the pharynx to the stomach


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Peristalsis

A series of

wave-like

contractions

that propelsfood along the

digestive tract

Q: What is it

called when

food moves

upwards?


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Structure of the Stomach

J-shaped muscular sac, stretches with food

3 layers of muscles: Longitudinal (outside), Circular

(middle) & Oblique (inner folds)

Inner lining is folded into accordion-like ridges called

rugae inc SA

Ridges contain gastric glands that produce gastric

juice (enzymes, mucus, HCl) for chemical digestion

Cardiac sphincter: ring of muscle controlling

entrance into stomach

Pyloric sphincter: ring of muscle controlling exit out

of stomach


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Stomach

Q: How many litres

of food can the

stomach hold when

fully expanded?

Q: How long does

it take your stomach

to empty after ameal?


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Bulk storage of undigested food

Mechanical breakdown of food via

rhythmic contractions (mixing of fluids)

Chemical Digestion: breaks chemical

bonds via hydrochloric acid (pH 2) and

enzymes (pepsin & lipase)

End product is chyme partially digestedfood in a semi-liquid state

Functions of the stomach


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Stomach Lining


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Mixing & Rhythmic Contractions


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Consist of a series of loops loosely attachedto the back of the abdomen

Name is from small diameter (approx. 2.5 to

3cm diameter, 7m in length) Mesentery: layer of connective tissue that

holds small intestine together to prevententangling of intestine in abdominal cavity

Ileocecal valve: ring of muscles (sphincter)that controls movement of material fromsmall intestine to large intestine

Structure of the Small Intestine


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3 Sub-regions of Small Intestine

Duodenum

Jejunum

Ileum


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Function of the Small Intestine

Most of the chemicaldigestion ofmacromolecules &absorption ofnutrients occurs here

90% of products areabsorbed in smallintestines

Other 10% absorptionoccurs in stomach &large intestines


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Structure of Intestinal Wall

Lining has folded finger-like projections

called villi increase SA

Each villus has many microscopic foldscalled microvilli further increase SA

to maximize absorption

Network ofcapillaries & tiny lymph vessel

called lacteal extend into hollow core ofeach villus


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The Intestinal Wall

*Note: only 2 layers of muscles (circular & longitudinal muscle)

instead of 3 like the stomach (no oblique muscle)


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Cross-section of Small Intestines


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Surface of Intestinal Wall


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Cross-section of Villus


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Absorption within Small Intestines

Nutrients are absorbed

across Intestinal cells

(Villus) either via the:

Blood Capillaries amino acids &

monosaccharides

Lacteal glycerol &

fatty acids


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Functions within each Region

Duodenum: (first 25cm, U-shaped)chemical digestion occurs here, chymemixes w/ digestive juices from pancreas,

liver, gall bladder & intestinal wall Jejunum: (~3m long) most absorption of

nutrients occur here, highly folded innerlining contains lots villi & intestinal glands

Ileum: (~4m long) contains fewer & smallervilli, absorb nutrients & push undigestedmaterial into large intestine


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Intestinal Movements

Peristalsis: series of

wave-like muscular

contractions &

relaxations Rhythmical

Segmentation:

mixing contractions

that knead materialback and forth without

propelling it forward at

a very fast rate


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Structure of the Large Intestine

Large upside-down U-shaped organ

Approx. 1.5m in length & 8cm in diameter

Three main sections: ascending colon,transverse colon & descending colon

Chyme enters caecum a small pouchconnected to ascending colon host to

large # of bacteria that breakdowncellulose

Appendix a finger-like projection at the tipof caecum function is still a mystery


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3 sections of the Large Intestine

Ascending

Transverse

Descending


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Complete absorption of nutrients

Reabsorb water, minerals & other useable

materials prevents dehydration

Absorb vitamins K & B (biotin, folic acid)

produced by bacteria (E. coli)

Form, compact & store fecal matter (waste &

undigested material) prior to defecation

*Note: movement of material via peristalsis

Functions of the Large Intestine


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Structure of the Large Intestines


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Last portion of the digestive tract:

Rectum: where feces are stored until

eliminated

Anal Canal: between rectum & anus

passageway for feces, ends in Internal

(involuntary) and External (voluntary) anal

sphincters allows body to control timingof elimination

Rectum & Anal Canal


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Digestive Questions

How long does it take to

digest a meal?

How is gas produced

within along thedigestive tract (2 ways)?

How does one get

diarrhea & how does it

happen?


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Accessory Organs

Pancreas, Liver &

Gall Bladder


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Accessory Organs

Large organs outside the digestive tract

that aids in chemical digestion

Chemical secretions are carried by ducts

that empties into the digestive tract

3 Main Accessory Organs:

Liver

Gall Bladder

Pancreas


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Liver, Gall Bladder & Pancreas


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Structure of the Liver

Largest internal organ, brownish-red in colour,divided into 2 large lobes (L & R)

Located just beneath the diaphragm


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Function of the Liver

Liver performs over 500 functions:

Produces bile (greenish-yellow liquid) that

contains bile salts from cholesterol that helps to

emulsify large fat globules into smaller fatdroplets (easier fat digestion & lipase action)

Emulsification: is a process that involves

molecules attracted to water at one end and fats

at the other end creating a suspension of smallfat dropletsstable emulsion

Bile released via hepatic duct


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Functions of the Liver

Plays major role in metabolism (set ofchemical reactions that maintains life):

Demolition: breaks down old RBC

Recycler: parts of decomposed Hb arerecycled to make bile salts

Storehouse: collects excess chemical inblood (i.e. fat soluble vitamins, glucose

glycogen)Detoxification centre: detoxifies poisons

ingested in food & water (i.e. alcohol)


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Hollow, pear-shaped organ on the

underside of the liver

Not involved in enzyme production

Storage warehouse for bile, release is

triggered by hormone via cystic duct

Gall Bladder


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Gall Bladder


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Structure of the Pancreas

Leaf-shaped gland, ~20cm in length

Located close to curve of stomach,

attached to the duodenum

Pancreatic juice enters duodenum via

pancreatic duct


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The Pancreas


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Produces over28 digestive enzymes thatbreaks down lipids (lipase), carbohydrates(amylase) & proteins (trypsin, peptidase)

Produces pancreatic juice, alkalinesubstance (NaHCO3) that neutralizesacidic chyme, so other enzymes canfunction

Produces insulin (hormone that regulatesblood glucose levels), allows glucose toenter cells

Pancreas


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Pancreas & Diabetes Hypoglycemic: abnormally low-levels of

glucose in blood (pancreas sends out too

much insulin to break down sugar)

Hyperglycemic: extremely high glucoselevels or diabetes (pancreas cant make

enough insulin or body cant use insulin)

Type 1: insulin dependent

Type 2: non-insulin dependent

Type 3: gestinational diabetes


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AccessoryOrgans &

their ducts


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Summary of the Digestive System

3d-Human Digestive System 2009

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