BI 203 Human Anatomy & Physiology II

BI 203 Human Anatomy & Physiology IIBI 203 Human Anatomy & Physiology II

Why do we have a digestive system?Provide nutrients to all tissues in the body

What is digestion?

Breakdown of organic molecules/nutrients... mechanical and chemical

What tasks does your digestive system do?

Ingestion, mastication, propulsion, mixing, secretion, digestion, absorption, transportation, elimination

Oral cavity

Pharynx

Esophagus

Stomach

Small intestinesPancreasLiver

Large intestinesRectumAnus

Organ Function Timeingestion/mastication 10-20 sec.secretion/mixing/digestion

transportation 1-2 sec.

transportation/propulsion 5-8 sec.

digestion/secretion 3-4 hrs.mixingdigestion/secretion/mixing 3-5 hrs.absorption/propulsion

absorption/propulsion 18-36 hrs.elimination

What happens between my mouth and anus?

BI 203 Human Anatomy & Physiology IIBI 203 Human Anatomy & Physiology II See Table 24.1

Graphic overview of alimentary canal

What structures exist between mouth and anus?


Graphic overview of …


What is the oral cavity and what does it do?

Ingestion (alternate routes)

Mastication = chewingWhich type of digestion? Why?Accomplished via: cheeks, lips, tongue, teeth, jaws

Vestibule: space between cheeks, lips and gums

Oral cavity proper:space within floor of mouth and roof (palate)

Types of teeth:IncisorsCaninesPremolarsMolars

deciduouspermanent

What is the oral cavity and what does it do?


Teeth embedded in:Alveoli in the Maxilla(upper jaw) & Mandible (lower jaw)

Closing jaw =massetertemporalismedial pterygoids

Opening jaw =lateral pterygoids

How do you masticate?


3 paired glands:ParotidSubmandibularSublingual

Scattered small tubular glands

How do you salivate?

Secrete mucus, serous fluid and enzymes

Endocrine or Exocrine?


Hard and Soft palates

Cleft lip/palate:congenital defect where embryonic tissues fail to fuse

“Because I was different” by Don Bartlette

What can your palate do for you ?


Food formed into a bolus

Pushed against hard palate by tongue

Initiates swallowing reflex

Pharyngeal muscles aid in pushing into esophagus

Swallowing (deglutition) divided into 3 phases:1) voluntary2) pharyngeal3) esophageal

Which of the pharynxes usually conduct food?

How does food get from oral cavity to esophagus?


Conducting Tube

~ 12” in length

2 sphincters:upper esophageal

lower esophageal or cardiac

Generalized layers of alimentary canal

1 2

3

4

What is the role of the esophagus?


Nerve plexus allows local reflexes to be integrated independent of the CNS.

Sensory neurons

Motor neurons

Interneurons

1 2

3

4

What is the role of the enteric plexus?


Varies in size

Rugae (wrinkles) allow distention

Entrance = gastroesophageal opening (cardiac)

Exit = pyloric opening

Muscularis different because 3 layers of muscle

DisordersHiatal hernia & Hypertrophic pyloric stenosis

Endoscopy

What’s unique about the stomique?


5 types of cells:

1) Surface mucous cells = mucus (1-1.5 mm, alkaline)

2) Mucous neck cells = mucus

3) Parietal cells = HCl, Intrinsic factor (B12)

How does gastric digestion occur?


5 types of cells:

4) Chief cells = pepsinogen, becomes pepsin in low pH, breaks covalent protein bonds, making peptides

5) Endocrine cells = hormones (gastrin), which stimulates secretory activity of parietal cells.

How does gastric digestion occur?

Gastric secretions and bolus form Chyme


How is gastric secretion regulated?Gastric secretion is divided into 3 phases:

1) Cephalic: Stimuli from head region initiate gastric secretion

2) Gastric: Stimuli from w/n stomach cause > secretion

3) Intestinal: Dependent on pH/chemistry of chyme in duodenum. > pH 3 then stimulates, < pH 2 then inhibits.


What is important about Liver anatomy?Largest internal organ, 2 major, 2 minor lobes

Connective tissue capsule invades at hepatic portal, form membrane bound lobules (6-sided), portal triads in corners


Bile production: formed in lobules, drains out hepatic ducts, secreted and/or stored in gall bladder.Storage: can store nutrients (glycogen, vitamins, fats)Nutrient interconversion: metabolically “swapped” DetoxificationPhagocytosisSynthesis

What’s the digestive role of the Liver?

What are gall stones?


Exocrine and endocrine functions

Pancreatic juice =

What’s the digestive role of the Pancreas?

Enzymatic component: enzymes essential for all food class digestion. Examples:trypsin = protein amylase = carboslipase = fatsribo and deoxyribonuclease = RNA/DNA


Pancreatic juice = Aqueous component H2O and HCO3-ions dilute & neutralize acidic chyme.

What is a source of bicarbonate ions?

What’s the digestive role of the Pancreas?


Long segment of alimentary canal… 6 meters

3 regions:

1) Duodenum

2) Jejunum

3) Ileum

What are the regions of the small intestines?


Contains features such as:

plicae circularis (circular folds)villimicrovilli

Why?

Functions include:

Digestion/Mixing/Absorption

What’s the internal anatomy of the small intestines?

Digestive enzymes in association w/ microvilli: disaccharidases, peptidases, nucleases


Divided into 4 regions:1) Ascending colonbegins at ileocecal valveends at hepatic flexure

2) Transverse colonbegins at hepatic flexureends at spleenic flexure

3) Descending colonbegins at spleenic flexureends at opening of pelvis

4) Sigmoid colonbegins at opening of pelvisends at rectum

RectumAnus Sphincters

What are the components of the colon?


SecretionAbsorption(form feces)

Normal flora can produce:

Vitamins (K)Flatus

Capable of mass movements

What are the functions of the colon?


How does it (defecation) happen?

Diarrhea & Constipation


•Mass movements

•Colic distension results in defecation reflex w/c is a contraction of rectal tunica muscularis and relaxation of internal anal sphincter.

•If ignored reflex is extinguished.

•If acted upon, voluntary actions result in defecation.

What is the big picture of digestion?

Bile

Small intestine enzymes


To understand Digestion and then absorption…

You need to know the component “pieces” molecules of each major nutrient group.

Water = H2O

Vitamins/Minerals = B12, Ascorbic acid (C) etc.

Salts = Positive ion (Ca2+) and negative ion (Cl-) CaCl2

Carbohydrates = Polysaccharides Disaccharides Monosac.

Lipids = triglycerides 3 fatty acids & gylcerol

Proteins = Polypeptides Dipeptides amino acids

What is the big picture of carbohydrate digestion?

Bile



Goal: Convert complex carbs (polysaccharides) and disacchrides into monosaccharides

1) Absorbed via 2ndary active transport

2) Facilitated diffusion to blood

3) Monosac. to liver to be converted to glucose and or glycogen

What is the big picture of lipid digestion?

Bile



Goal: Convert to fatty acids, glycerol

1) Micelles formed

2) Attach to plasma membrane, lipid components diffuse into epithelium

3) Changed back into triglycerides and coated with proteins. Chylomicrons excreted

4) Chylomicrons move to lacteal, then blood stream


Bile



What is the most dense?

Water

Lipids

Proteins


Bile



Bile



Goal: Form amino acids

1) Amino acids absorbed via 2ndary active transport and/or diffusion

2) A.a. moved out via active transport

3) Enter blood stream and move to liver

What is the big picture of protein digestion?

Pepsin =


polypeptides


Trypsin =

Chymotrypsin =

Carboxypeptidase =


oligopeptides

oligopeptides

amino acids


Carboxypeptidase =

Aminopeptidase =

Dipeptidase =


amino acids

amino acids

amino acids


What is the big picture of digestion?

Saliva

Gastric juice

Pancreatic juice

Bile


Carbos Proteins Lipids

amylasePolysacc. Disacc.

Monosacc.

Disacc.amylase

SucraseLactase

Poly, di peptides

tri, di peptides, a. a.

pepsin

trypsin

peptidaseGlycerol, fatty acids

lipase, esteraselipase

bile salts


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BI 203 Human Anatomy & Physiology II

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