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Anatomy and Physiology 1111 > Module 18 > Flashcards

Module 18 Flashcards

1
Q

Digestive System Parts

A

The digestive system comprises:

Gastrointestinal tract (GI tract)

  • also called alimentary canal
  • think of the journey traveled by a seed as it travels from guzzle to zatch

Associated Organs

  • teeth
  • tongue
  • salivary glands
  • liver
  • gallbladder
  • pancreas
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2
Q

What are the 6 Functions of the Digestive System?

A
  1. Ingestion: to take in food
  2. Secretion: to release substances that will help in the breakdown and absorption of nutrients
  3. Mixing and propulsion: ensuring that chemicals and foods are mixed to promote breakdown and moving things along
  4. Digestion: breaking down foods
  5. Absorption: transferring nutrients from the GI tract to the bloodstream
  6. Defecation: removing waste matter from the body
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3
Q

What are the 4 Layer of the GI Tract?

A

The structure of the GI tract is basically the same throughout. The four layers deep to superficial from the lumen out:

  1. mucosa
  2. submucosa: areolar connective tissue
  3. muscularis: also called muscularis externa to distinguish it from the thinner, weaker muscle layer of the mucosa.
  4. serosa: in the abdomen, the serosa forms part of the peritoneal cavity.
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4
Q

Mucosa

A

The mucosa is the layer that lines the lumen. It has 3 sublayers in order from the lumen out:

  • epithelium, stratified squamous in the mouth and simple columnar in the stomach and intestines
  • lamina propria, a layer of areolar connective tissue with blood and lymphatic vessels to pick up material absorbed by epithelium.
  • muscularis mucosae, a thin muscle layer that makes the inside of the GI tract all crinkly and folded.
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5
Q

Submucosa

A

The submucosa comprises areolar connective tissue. In it, we find blood and lymphatic vessels and the submucosal plexus of the enteric nervous system.

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6
Q

Muscularis

A

Striated (voluntary) muscle in the mouth and pharynx controls swallowing. Smooth (involuntary) muscle, usually in two layers, lines the rest of the GI tract and keeps materials moving through peristalsis.

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7
Q

Serosa

A

The serosa is made up of areolar connective tissue covered by a simple squamous epithelium (mesothelium). In the abdominal cavity, the serosa is called the visceral peritoneum (Latin viscera: “bowels”) because it forms the “guts” (visceral) side of the peritoneal cavity.

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8
Q

Overview of the Oral Cavity

A

Teeth

  • molars
  • premolars
  • bicuspids
  • cuspids (canines)
  • incisors
Tongue
Uvula
Pharynx
Hard palate
Soft palate
Palatine tonsils
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9
Q

Borders of the Oral Cavity

A

The borders of the oral cavity are the:

  • cheeks, or buccal surface (Latin bucca: “cheek”), forming the sides
  • hard and soft palates, forming the “roof” and
  • tongue, or lingual surface (Latin lingua: “tongue”) forming the “floor”
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10
Q

Buccal

A

Toward the cheek

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11
Q

Lingual

A

Toward the tongue

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12
Q

Occlusal

A

For teeth, towards the surface where they meet other teeth

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13
Q

Mesial

A

Toward the midline

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14
Q

Distal

A

Farther away from the midline

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15
Q

What are the 4 Shapes of Teeth?

A

There are 4 shapes of teeth that are used as part of the full names of teeth:

  • incisors (Latin incisus: “cut into”): sharp cutting teeth
  • cuspid (canine) teeth (Latin cuspis: “point, spear”)
  • premolars (bicuspids)
  • molars (Latin molere: “grindstone”)
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16
Q

Permanent Teeth

A

There are 32 teeth in a human mouth: 8 upper right, 8 upper left, 8 lower right, 8 lower left. The maxilla refers to the upper jaw, and mandible to the lower jaw

Numbers starts with the most distal maxillary molar on the patients right. The numbers continue around the upper jaw until the most distal left maxillary molar. Then, the numbers continue on the left side with the most distal left mandibular molar and around to the most distal right mandibular molar,

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17
Q

Upper Teeth and Lower Teeth

A
  1. 3rd Molar (wisdom tooth) 17
  2. 2nd Molar (12yr molar) 18
  3. 1st Molar (6yr molar) 19
  4. 2nd Bicuspid (2nd premolar) 20
  5. 1st Bicuspid (1st premolar) 21
  6. Cuspid (canine/eyetooth) 22
  7. Lateral incisor 23
  8. Central incisor 24
  9. Central incisor 25
  10. Lateral incisor 26
  11. Cuspid (canine/eyetooth) 27
  12. 1st Bicuspid (1st premolar) 28
  13. 2nd Bicuspid (2nd premolar) 29
  14. 1st Molar (6yr molar) 30
  15. 2nd Molar (12yr molar) 31
  16. 3rd Molar (wisdom tooth) 32
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18
Q

Deciduous Teeth (Children)

A

In children, teeth begin to erupt at about 6 months. Children have only 20 deciduous teeth (Latin decidere: “to fall off” - the same as deciduous trees lose their leaves)

Teeth are listed A-T.

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19
Q

What are the 3 Parts of the Tooth?

A

From top to bottom:

  1. Crown: the part of the tooth above the gumline and visible
  2. Neck: the part just below the gumline
  3. Root: the part that attaches the tooth to the periodontal ligaments and then to the jawbone (maxilla or mandible).
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20
Q

What are the Structures of the Tooth?

A
  • enamel
  • dentin
  • dentinal tubules
  • cementum
  • pulp cavity
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21
Q

Enamel

A

The outer part of the tooth forming the occlusal surface and the contacts between teeth. It’s made up of calcium, phosphate, and calcium carbonate. Enamel is harder than bone, because it is almost all mineral with little organic matrix

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22
Q

Dentin

A

Is below the enamel and forms the bulk of the tooth. It is also harder than bone, but not as hard as enamel.
- Also, dentin contains dentinal tubules which allow fluid to move. Normally, the enamel covers dentin and keeps fluid from moving. When the dentin is exposed, fluids can move and the nerves of the root send a strong pain signal to the brain.

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23
Q

Cementum

A

The dentin of the root is covered by cementum and is connected to bone by a series of periodontal ligaments, a dense fibrous connective tissue. The periodontal ligaments have proprioception (pressure receptive nerves) and are resistant to anesthesia, which is why we can feel the pressure on our teeth from dental work even when the pain fibers are quiet.

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24
Q

Pulp Cavity

A

The pain fibers and blood vessel are enclosed in the pulp cavity, a chamber formed by dentin with one to three outlets (apical foramina), one for each tooth root. Pain signals carried by these nerve fibers are carried on the trigeminal nerve (cranial nerve V).

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25
Q

Tongue

A

The tongue forms the floor of the oral cavity. It is skeletal muscle with a mucous membrane. It also functions as a taste organ. Individual taste buds cover the entire surface of the tongue,

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26
Q

What are the 3 Groups of Taste Buds on the Tongue?

A

Several gustatory receptor cells and supporting cells are clustered in each taste bud:

  1. Fungiform papillae
  2. Foliate papillae
  3. Vallate papillae

Also scattered taste buds on lips, palate, and oropharynx

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27
Q

Filiform Papillae

A

Look like little threads (Latin filum: “thread”). They cover most of the tongue surface. These are non-taste structures that give the tongue a rough texture.

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28
Q

Fungiform Papillae

A

(Latin fungus: “mushroom”) Look like little mushrooms

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29
Q

Foliate Papillae

A

(Latin folium: “leaf”) Are leaf-shaped papillae found along the lateral surface of the posterior tongue.

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30
Q

Vallate (or Circumvallate) Papillae

A

(Latin vallatus: “surrounded by a wall”) Form a V-shaped row along the poterior tongue. There are usually 7-12 of these, and it’s easier to see them on a friend’s tongue than on your own.

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31
Q

Tongue Anatomy

A

Papillae

  • Filiform
  • Fungiform
  • Foliate
  • Vallate

Muscle

Taste buds (blue)

Lingual Glands: tongue has a set of these. They secrete mucous plus an enzyme, lingual lipase, which helps break down patty foods in the mouth.

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32
Q

What are the 3 Main Salivary Glands?

A
  • Parotid gland: the largest gland, inferior and anterior to the ears, parotid duct
  • Sublingual gland: beneath the tongue, lesser sublingual ducts
  • Submandibular gland: floor of the mouth medial and inferior to the mandible, submandibular ducts

Duct names copy the gland name.

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33
Q

What are the 4 Minor Salivary Glands?

A
  • labial
  • buccal
  • palatal
  • lingual
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34
Q

What are the 2 Types of Acini Found in Salivary Glands?

A

Microscopically, there are 2 kinds of acini (cell groupings) found in salivary glands:

  • Mucous acini: make mucus
  • Serous acini: make enzymes in a watery fluid
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35
Q

What are the 3 Types of Enzymes in Saliva?

A

Saliva is almost all water (99.5%). The remaining part is mucus and enzymes. Enzymes in the saliva include:

  • Lysozyme: breaks down invading microbes
  • Immunoglobulin A (IgA): Recall that IgA is the immunoglobin found in the body’s secretions
  • Salivary amylase (Latin amylum: “starch”) This enzyme begins the breakdown of starchy foods into sugars, which is why starchy foods (such as potatoes) taste sweet, even though they have little free sugar; the sugar is released by salivary amylase.
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36
Q

How do the 3 Salivary Glands Differ in their Secretions?

A
  • The parotid gland has more serous acini, therefore makes water + enzymes
  • The submandibular gland has both serous and mucous acini, therefore makes water + mucous+ enzymes
  • The sublingual gland has mostly mucous acini, therefore, mucous with few enzymes
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37
Q

What are the 3 Divisions of the Pharynx?

A

The pharynx is the point of transition between the oral cavity and the esophagus. It is divided into 3 parts:

  • nasopharynx: connects the paranasal sinuses to the pharynx, allowing air to pass from the nose to the trachea.
  • oropharynx: joins the nasal cavity and oral cavity to the gut tube and trachea
  • laryngopharynx: is adjacent to the larynx (“voicebox”). Here, the epiglottis covers the trachea when swallowing food and drink, and covers the esophagus when breathing.
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38
Q

Esophagus

A

Is simply a muscular tube that moves food from the pharynx to the stomach, it doesn’t have an absorptive surface.
- The epithelial sublayer of the mucosa is a nonkeratinized stratified squamous epithelium. The muscularis mucosae of the mucosa is relatively thick.

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39
Q

What are the 2 Layers of the muscularis of the Esophagus?

A

The 2 layers of the muscularis are:

  • circular layer: closes off the lumen when contracted
  • longitudinal layer: contracts in waves (peristalsis) to move things along.
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40
Q

Esophagus: Control of Deglutition

A

Esophagus Borders

  • upper esophageal sphincter: between the pharynx and esophagus
  • lower esophageal sphincter: between esophagus and stomach

Voluntary
- upper esophageal sphincter and first third (5cm) is striated muscle

Involuntary
- lower 2/3 of esophagus and lower esophageal sphincter is smooth muscle

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41
Q

What are the 3 Stages of Deglutition ?

A

Deglutition is the process of swallowing. Swallowing has 3 phases:

  1. Voluntary: the stage we control consiously
  2. Pharyngeal: when the bolus of food is in the oro - and laryngopharynx. This is the stage where food and water are kept out of the trachea.
  3. Esophageal: the upper esophageal sphincter opens, and the autonomic process of peristalsis begins.
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42
Q

What are the 5 Regions of the Stomach?

A

Food and liquid leaving the esophagus pass through the lower esophageal sphincter (cardiac sphincter) as they enter the stomach. The stomach has 5 regions and 2 curves:

Regions:

  • Cardia
  • Fundus
  • Body
  • Pyloric antrum
  • Pyloric canal

Curves:

  • Greater curvature
  • Lesser curvature
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43
Q

GERD

A

The lower esophageal sphincter sometimes fails to tightly close, causing a condition called gastro-esophageal reflux disease (GERD). GERD can be caused by increased abdominal pressure, as in obesity.

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44
Q

Cardia

A

A region of the stomach

The cardia is the point at which the esophagus crosses the diaphragm to become the stomach.

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45
Q

Fundus

A

A region of the stomach

The fundus comes from the same word as “foundation”, and describes any structure that you can see like the bottom of a bottle viewed through the neck of the bottle.

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46
Q

Body

A

A region of the stomach

The bulk of the stomach is the body.

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47
Q

Pyloric Antrum & Pyloric Canal

A

The narrower part nearest the small intestine is the pylorus. (Latin: “gatekeeper”) The pyloric antrum (Latin: “cave”) transitions into the pyloric canal.

At the end of the pyloric canal is the pyloric sphincter, which represents the end of the stomach and outlet for stomach contents. The pyloric sphincter opens into the duodenum (Latin: “12 finger breadths”) which is the inital segment of the small intestine.

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48
Q

Greater and Lesser Curvature

A

The stomach is a curved bag, and the smaller of the two curves is called the lesser curvature, while the larger arc is the greater curvature.

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49
Q

Histology of the Stomach

A
  • Mucosa Layer: is specialized for the digestion of food. The specialization takes the form of gastric pits.
  • Gastric Glands: each of these depressions in lined with simple columnar epithelium. The bottom half of each gastric pit has a higher concentration of glandular cells that collectively are called the gastric glands.
  • Along the stomach lumen, epithelial cells and surface mucous cells predominate. Mucus is an essential part of the stomach lining, and protects the cells on the surface from being damaged by the acid and enzymes secreted by teh stomach.
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50
Q

Cell Types of the Stomach

A

Mucous Secreting C ells

  • surface mucous cells: secrete protective mucous
  • mucous neck cells

Specialized Cells

  • parietal cells
  • secrete HCI
  • secrete intrinsic factor (vitamin B12)

Enzyme-Secreting Cells

  • chief cells
  • secrete pepsinogen, lipase

Enteroendocrine Cells

  • G cells
  • secrete gastrin
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51
Q

Parietal Cells

A

A type of Specialized Cell

Have two essential roles:

  • First, they have specialized protein pumps that dump H+ and Cl- ions into the lumen, make HCI - stomach acid
  • Second, they secrete intrinsic factor which is critical for absorbtion of vitamin B12 which is needed for red bood cell production. Decreased production of intrinsic factor leads to pernicious anemia - abnormal red blood cells.
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52
Q

Chief Cells

A

An enzyme-secreting cell

Chief cells secrete the enzymes pepsinogen and lipase.

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53
Q

G Cells

A

A type of Enteroendocrine cell

G cells are an examples of enteroendocrine cells, a kindof hormonal system in the GI tract. They secrete the hormone gastrin.

54
Q

Muscularis Layer

A

Another special feature of the stomach is the presence of an “extra” layer in thick muscularis: the oblique muscle layer with fibers running diagonally. This layer aids in the stomach’s ability to “churn” substances and speed digestion.

55
Q

HCI Secretion by Parietal Cells of the Stomach

A

Parietal cells of the stomach secrete hydrochloric acid (HCI) to aid in digestion and protect from invaders,

Make H+ ions (protons)

  • water + CO2 makes carbonic acid (H2CO3) which then buffers to H+ and HCO3- (bicarbonate ion)
  • H+ pumped out, K+ pumped in by active transport (H+/K+ ATPase)

Make Cl- ions

  • Cl- concentrated in cell by antiporter (dumps HCO3- into bloodstream)
  • Cl- concentration high in parietal cell, flows into stomach lumen through Cl- channel
56
Q

Regulation of HCI Release

A

Several neurotransmitters/hormones up-regulate HCI secretion:

  • acetylcholine from parasympathetic stimulation (vagus)
  • gastrin from G cells
  • histamine from mast cells in the lamina propria (via H2 receptors)
57
Q

Ulcers

A

Disease can increase secretion of stomach acid, or more commonly, decrease the secretion of protective materials (such as mucous). When this happens, the stomach has an increased tendency to ulcerate.

Bacterium Helicobacter pylori disrupts the secretion of protective mucus and predisposes patients to gastric ulcers. Failure of the pancreas to make bicarbonate can result in duodenal ulcers.

58
Q

Proton-pump Inhibitors (PPIs)

A

One class of drugs acts by inhibiting the proton pump (H+/K+ ATPase). Examples of these proton-pump inhibitors include:

  • omeprazole (Prilosec)
  • lansoprazole (Prevacid)
  • esomeprazole (Nexium)
59
Q

What are the 3 Regions of the Small Intestine?

A

From stomach to large intestine:

  • duodenum (Latin: “12 finger breadths”), about 0.25 m in length
  • jejunum (Latin: “empty”), about 1 m long
  • ileum (Latin: “flank”), about 2 m long

The lumen is wrinkly, with plicae circularis, the Latin name for “circular folds”.

60
Q

Small Intestine

A

In the mucosa, the epithelial layer consists of a simple columnar epithelium. The shape of these cells allows them to absorb water and nutrients on their apical (luminal surfaces).

For this reason, the lamina propria of the mucosa has a rich capillary bed, with numerous arterioles and venules. Also, a small lymph vessel called a lacteal carries lipids from the absorptive epithelium. These lymphatics evenutally gather into the thoracic duct which, in turn, releases into the bloodstream and left jugular/subclavian junction.

the muscularis layer reverts to the “normal” two sublayers of smooth muscle fibers: a circular and a longitudinal layer. Between them lie clusters of neurons that control autonomic movements of the intestines: the myenteric plexi. These neurons generate the peristaltic waves that keep things moving in the GI tract.

61
Q

Cell Types of the Small Intestine

A

Cells Lining the Villus:

Mucus-Secreting Cells
- goblet cells

Specialized Cells

  • absorptive cells
  • absorb nutrients
  • microvilli increase surface area for absorption

Enzyme-Secreting Cells

  • Paneth cells
  • secrete lysozyme
  • can phagocytose

Enteroendocrine Cells
- secrete secretin, CCK, GIP

62
Q

Luminal Surface of Small Intestine

A

The luminal surface of the small intestine appears velvety. This is because of the presence of villi (Latin: “shaggy”), These finger-like projections are about 1 mm long by 0.1 mm diameter.
- Most of the villi’s epithelial cells are specialized for absorption. These cells are coated with microvilli, a smaller version of the villi.

63
Q

Paneth Cells

A

An enzyme-secreting cell

They secrete many enzymes and are also capable of phagocytosis.

64
Q

Enteroendocrine Cells

A

Enteroendocrine cells of the intestine secrete secretin from S cells, cholecystokinin (CCK) from CCK cells, and glucose-dependent insulinotropic peptide (GIP) from K cells.

65
Q

Specialization of the Small Intestine

A

At every level, the small intestine is specialized to increase surface area.

  • plicae circularis
  • villi
  • microvilli

All these folds and shag carpets and microscopic fingers are aimed at increasing the surface area of the small intestine. Since the surface is covered with an epithelium of (mostly) absorptive cells, this increased surface area increases the area available for absorption of water and nutrients.

The absorptive cells, on the other hand, are covered with protein channels that bring substances from the lumen into the absorptive cell by symport systems that carry Na+ and and glucose, or Na+ and amino acids, into the intestinal cell at the same time

66
Q

Absorption of Nutrients: Sugars

A

Sugars:

  1. Enzymes convert di and polysaccarides to glucose, galactose, and fructose
  2. Glucose, galactose pumped into the intestinal cell cytoplasm; fructose moves into intestinal cell cytoplasm by facilitated diffusion
  3. From intestinal cell to bloodstream by facilitated diffusion.

The only moosaccarides absored by intestinal cells are glucose, galactose, or fructose.

67
Q

Absorption of Nutrients: Proteins

A

Proteins:

  1. Enzymes convert proteins to amino acids, di-, tripeptides
  2. These pumped into intestinal cell cytoplasm by active transport
  3. From intestinal cell to bloodstream by simple diffusion.
68
Q

Absorption of Nutrients: Fats (Lipids)

A

Fats (Lipids):

  1. Short-chain fatty acids - simple diffusion from lumen to intestinal cell cytoplasm to bloodstream
  2. Long-chain fatty acids and monoglycerides:
    - insoluble in water: carried in bloodstream in balls called micelles
    - move into intestinal cell cytoplasm by simple diffusion
    - intestinal cell forms these into triglycerides, which are packaged in chylomicrons and dumped into lacteals (lymph vessel in core of villus).
69
Q

After Absorption of Nutrients

A

All these molecules enter hepatic portal circulation
- Except lipids as chylomicrons in lymphatic drainage: lymph drains into thoracic duct, then enters bloodstream via left subclavian vein.

70
Q

Vitamins in the Digestive System

A

Vitamins work to speed up essential chemical reactions in cells by lowering the activation energy of chemical reactions. Vitamins are non-protein catalysts.

Water-soluble vitamins (B, C, niacin, biotin, folic acid) absorbed directly by stomach and intestines.

Fat-soluble vitamin K make by bacteria in large intestine, aids in blood clotting

Water-soluble vitamin B12 absorbed with help of intrinsic factor secreted by parietal cells of stomach

71
Q

Pernicious Anemia

A

Disruption of normal intrinsic factor production by diseases of the stomach results in pernicious anemia, a macrocytic anemia. In this disease, RBCs are too large and low in number.

72
Q

What are the Regions of the Large Intestine?

A
  • Cecum: vermiform appendix
  • ascending colon
  • transverse colon
  • descending colon
  • sigmoid colon
  • rectum
  • anal canal / anus
73
Q

Ileocecal Sphincter

A

The large intestine begins where the ilium (final portion of the small intestine) has an outlet through the ileocecal sphincter into the cecum.

74
Q

Cecum

A

Latin: “blind [pouch]” The cecum is a classic example of bad design. Not only does it tend to catch objects that have passed into the large intestine, but it ends in the vermiform appendix (or just appendix)

75
Q

Appendix

A

Is a small, worm-like tube that often becomes inflamed and may even burst, dumping the bacteria-laden intestinal contents into the peritoneal cavity, a medical emergency.

76
Q

Colon (Large Intestine):

A

Like the small intestine, the colon has a velvety appearance with numerous microvilli. There are openings for intestinal glands (crypts of Lieberkuhn).

77
Q

What are the 2 Cell Types of the Colon?

A

Cells lining the intestinal glands (crypts of Lieberkuhn). The only 2 cell types present are goblet cells and absorptive cells.

Mucus-Secreting Cells
- goblet cels

Specialized Cells

  • absorptive cells absorb water
  • microvillio increase surface area for absorption

Enzyme Secreting Cells

  • None: digestions is carried out by bacteria
  • Some B vitamins and vitamin K made by cavteria
78
Q

Anal Sphincters

A

The rectum ends in anal canal and anus. There are 2 sphincters in the anus:

  • Internal anal sphincter: involuntary sphincter; autonomic motor, smooth muscle
  • External anal sphincter: voluntary sphincter; somatic motor, skeletal muscle
79
Q

The Defecation Reflex and Its Control

A

Elimination is the removal of wastes from the body by expelling material from the anus

Defecation Reflex: Like swallowing, the defecation reflex is a mixture of autonomic and voluntary motor control. It is triggered by distension (enlargement) of the rectum. (e.g. enema to trigger defecation)

Activation of stretch receptors in the wall of the rectum lead to internal anal sphincter relaxation (involuntary). This can be overridden by the external anal sphincter, which is controlled by the cortex of the brain (voluntary).

80
Q

Valsalva Maneuver

A

In the Valsalva Maneuver, the patient tries to exhale against a closed nose and mouth while bearing down (as in a bowel movement)

  • This increases abdominal pressure and results in characteristic changes in blood pressure and heart rate.
  • Can be used to diagnose heart disease
  • This can also correct atrial fibrillation in some cases
81
Q

What are the 4 Lobes of the Liver?

A

The liver is tied with the brain as the second-largest organ of the body. It is divided into 4 lobes:

  • Right Lobe
  • Left Lobe
  • Caudate Lobe (“tail shaped”)
  • Quadrate Lobe (“square”)
82
Q

What are the 3 Ligaments of the Liver?

A

The liver is held in place by three strips of connective tissue called ligaments:

  • falciform ligament (“sickle-shaped”): Attach ed to the diaphragm, divides the left lobe from the right, caudate, and quadrate lobes.
  • coronary ligament: Superior to the liver, attached to the diaphragm to keep the liver in a position in the superior part of the abdominal cavity, and mostly to the right.
  • round ligament (ligamentum teres)
83
Q

Liver: Blood Supply

A

The liver receives blood from digestive organs for:

  • detoxification
  • adding essential proteins

Has a Dual Blood Supply:

  • oxygenated blood from heart via hepatic artery
  • deoxygenated blood with absorbed nutrients from digestive organs via hepatic portal vein.
84
Q

Liver: Incoming Blood

A
  • Blood from the heart arrives via the hepatic artery. The cells of the liver need this oxygen from the heart.
  • Blood from digestive organs arrives via the hepatic portal vein. The blood here goes through detoxification and energy from it is stored. This supply comes from a venous drainage of the stomach and intestines through a vessel called the hepatic portal vein. This brings glucose-rich but oxygen-poor blood from the abosorptive cells of the digestive organs to the liver for processing.
85
Q

Liver: Outgoing Blood

A
  • Blood minus toxins plus proteins made by liver is dumped into the hepatic vein which goes to the heart via the inferior vena cava.
86
Q

Liver Lobules: Flow of Blood Steps through the Liver

A
  1. Oxygenated blood from hepatic artery OR Nutrient-rich deoxygenated-bood from hepatic portal vein
  2. Liver sinusoids
  3. Central vein
  4. Hepatic vein
  5. inferior vena cava
  6. Right atrium of heart.
87
Q

What are the 2 Main Cell Types in the Liver?

A
  • Hepatocytes: inactivate toxins, produce bile, and also produce a variety of blood proteins. Also play a role in the metabolism of carbohydrates, lipids, and proteins.
  • Kupffer Cells: are just a special name for a type of macrophage found in the liver. They destroy aged red blood cells and any invaders that reach the liver from the intestinal drainage.
88
Q

Bile

A

One of the jobs of hepatocytes is to produce bile, a greenish liquid substance that is stored in the gallbladder.

  • When bile is released into the GI tract, it helps to emulsify fats so they can be transported across the intestinal cell and dumped into the lymph vessel (lacteal) in the center of each villus.
  • Bile is produced and secreted by hepatocytes, and it travels in tiny vessels called bile canaliculi to join together as a bile duct.
89
Q

The Portal Triad: Hepatic Triad

A

The structures seen together at 3 of the 6 “corners” of the lobule are:

  1. Branch of hepatic portal
  2. Branch of hepatic artery
  3. Bile duct.

Together, these are called the portal triad (or hepatic triad).

90
Q

Bile Production, Storage, and Release Steps

A
  1. Bile produced by hepatocytes
  2. Bile Canliculi
  3. Bile Duct (as part of Portal Triad)
  4. Right and Left Hepatic Ducts
  5. Common bile duct
  6. Cystic duct (leads to gall bladder)
  7. Storage in gall bladder or release to small intestine.

If bile is stored, and GI tract signals presence of fats in a meal, the smooth muscle of gallbladder squeezes to release stored bile into cystic duct (again), and into the common bile duct which joins pancreatic duct at hepatopancreatic ampulla.

91
Q

Hepatopancreatic Ampulla

A

(Latin: “bottle”) The ampulla is a mixing chamber for pancreatic juices and bile; the sphincter controls release of this mixture into the duodenum.

92
Q

Enterohepatic Circulation of Bile Salts

A

Recall that 85% of the body’s heme is found in red blood cell hemoglobin. Heme is constantly being broken down. The spleen (and other cells) use the enzyme “heme oxygenase” to convert heme to biliverdin.

Biliverdin spontaneously converts into bilirubin. Bilirubin made this way is referred to as “unconjugated”; it gloms into the blood protein and is carried to the liver.

93
Q

Unconjugated Bilirubin

A

Unconjugated Bilirubin is insoluble in blood. In the liver, it is conjugated to the small molecule glucuronic acic, making it water-soluble. In this form, it makes up a major portion of bile.

Conjugated Bilirubin ends up in several places:

  • Converted to urobilinogen, it travels in the blood circulation. A small amount is processed by the kidneys and gives urine its characteristic yellow color.
  • Conjugated bilirubin in bile is released into the intestines where it is converted to stercobilin, which has a brown color ad gives its brown color to feces.
94
Q

What are the 2 Problems that May Arise in the Circulation of Bile Salts?

A

Problems arise when this well-oiled machine goes off the rails:

  1. Bile Obstruction
  2. Jaundice
95
Q

Bile Obstruction

A

If the bile is obstructed, then it can no longer release in normal quantities through the hepatopancreatic sphincter. In this case, little or no conjugated bilrubin is converted to stercobilin and the feces are pale in color.

At the same time, urobilinogen accumulates in urine, which gives it a darker than normal color.

96
Q

Jaundice

A

The liver may be incapacitated, for example by a virus (hepatitis), or by drug or alcohol abuse.

In newborns, the liver has to switch over from its role of making red blood cells to its digestive roles, and sometimes this changeover does not occur smoothly.

In any of these cases, bilirubin cannot be conjugated, and the skin and especially the “whites” of the eyes become noticeably yellow. This is called jaundice. The yellow color is from accumulation of unconjugated bilrubin.

97
Q

What are the 5 Islet Cells of the Pancreas?

A

The pancreas is at least two organs in one, with 2 functions:

  1. Endocrine Pancreas: Endocrine system = islets
  2. Exocrine Pancreas: Digestive function = acini

Pancreatic Islets house the endocrine pancreas. The 5 Islet cells are:

  • alpha cells (1/6): glucagon
  • beta cells (3/4): insulin
  • delta cells (1/12): somatostatin
  • F cells or PP cells (1/20): pancreatic polypeptide
  • epsilon cells (<1/100): ghrelin
98
Q

Ghrelin

A

An increase in ghrelin increases appetite. Mice that are genetically altered to interfere with the ghrelin system are not only skinny, but they live longer.

99
Q

The Exocrine Pancreas

A

The pancreas is about 99% acini and 1% islets. Acini secrete pancreatic juices which neutralize stomach acids:

Sodium bicarbonate: to buffer stomach acid (similar to baking soda)

Amylase: a starch-digesting enzyme.

Protein-Digesting Enzymes:
- Trypsin, chymotrypsin, carboxypeptidase, and elastase

Fat Digesting Enzymes:
- Pacreatic Lipase

RNA & DNA Digesting Enzymes:
- Ribonuclease and deoxyribonuclease

100
Q

What are the 3 Phases of Digestion?

A
  1. Cephalic Phase
  2. Gastric Phase
  3. Intestinal Phase
101
Q

Cephalic Phase

A

Stimulus: smell, taste, sight, or thought of food.

Action: brain prepares body for a meal

Result: CN VII, CN IX stimulate salivation; CN X stiulates stomach acid secretion.

102
Q

Gastric Phase

A

Stimulus: stomach wall stretches or pH increases

Action: increase gastric motility and secretion of HCI

Result: stomach empties into duodenum as food is digested

Hormonal regulation: by gastrin secreted from G cells.

103
Q

Intestinal Phase

A

Stimulus: Chyme in duodenum

Action: Activation of enterogastric reflex

Result:

  • Stretch receptors in duodenal wall signal medulla
  • Medulla inhibits parasympathetic ACh release from vagus
  • Decreased gastric motility, Increased tone in pyloric sphincter. More chyme stays in stomach, less enter duodenum. (note: this is an example of a long reflex)

Hormonal Regulation: cholecystokinin (CCK) and secretin from duodenum.

104
Q

Gastrin

A
  • Made by: G cells of stomach
  • Acts on: stomach
  • Action: promotes secretion of gastric juices
105
Q

Cholecystokinin (CCK)

A
  • Made by: enteroendocrine cells of small intestine
  • Acts on: gallbladder, pancreas, and brain
  • Action: ejection of bile; opening of sphincter of hepatopancreatic ampulla; more pancreatic juice, feel full
106
Q

Secretin

A
  • Made by: enteroendocrine cells (“S cells”) of duodenum
  • Acts on: pancreas
  • Action: more bicarb in pancreatic juice
107
Q

Glucose-Dependent Insulinotropic Peptide (GIP)

A
  • Made by: enteroendocrine cells (“K cells”) of duodenum and jejunum
  • Acts on: beta cells of pancreatic islets
  • Action: increases insulin secretion
108
Q

Histamine

A

Made by: mast cells of lamina propria
Acts on: parietal cells of stomach
Action: increases acid secretion

109
Q

Somatostatin

A

Made by: hypothalamus
Acts on: many digestive organs
Action: decreases exocrine pancreas, decreases many hormones, and slows gastric emptying.

110
Q

Motilin

A

Made by: enteroendocrine cells (“M cells”) of duodenum and jejunum.
Action: Increases migrating myoelectric complex, increases pepsin, and increases bowel motility.

111
Q

Peristalsis

A

Peristalsis is a traveling wave of contraction.

  • A section of bowel contracts, pushing bolus out
  • At the same time, adjacent section relaxes and bolus squirts from area of high pressure to low pressure (like toothpaste)
  • This process is controlled by the autonomic nervous system that resides in the bowel wall (myenteric and submucosal plexi)
112
Q

Mass Movement

A

Peristalsis results in mass movement.

  • If pressure is recorded at a single location, peristalsis looks like waves of contraction and relaxation
  • If electrical activity is measured at a single point, see spikes with each contraction (a migrating myoelectric complex)
  • These waves of electrical activity lead to smooth muscle contraction. Pressures are created by the activity of the enteric nervous system.
113
Q

Segmentation

A

The alternating contraction and relaxation of the mass movement.

114
Q

The Myenteric Plexus

A

Controls motor neurons innervating the longitudinal and circular muscle layers of the muscularis.

Receives sensory information from the GI tract

115
Q

Submucosal Plexus

A

The myenteric plexus also sends axons to the submucosal plexus, where motor neurons innervate the small, weak muscles that give the mucosal epithelium its wrinkles.

Receives sensory information from the GI tract

116
Q

Absorption of Water in the GI Tract

A

Intestines are responsible for absorbing water. Accounting for liquids in the GI tract:

  • Ingestion = 2.3L
  • Secretion = 6.0L
  • Total daily input = 9.3L
  • Small Intestine absorbs 8.3L
  • Large Intestine absorbs 0.9L
  • Feces (about 0.15L/day) contains about 0.1 L water
117
Q

What 3 Factors can Increase Bowel Motility?

A

Laxatives act by increasing GI motility. Increased motility means faster transit time from mouth to anus and therefore, less absorption of water and nutrients. Factors that increase bowel motility include:

  1. Chyme volume: an increase in chyme volume increases motility.
  2. Chemical composition: chemicals that increase electrical activity, for example by activating sensory nerves of the GI epithelium, increase motility
  3. Osmolarity: if non-absorbable chemicals (such as those found in sugar-free candies or some laxitives) are higher than 300 mOsm/kg (blood tonicity), water is “drawn” into the lumen.
118
Q

What are the 2 Components of Digestion?

A
  • Mechanical Digestion: mixing and tearing forces
  • Chemical Digestion: chemicals and enzymes acting on food

Each organ participates in both types of digestion.

119
Q

Organ “wrinkles” that Help in Mixing Process of Mechanical Digestion

A
  • Stomach: rugae (Latin ruga: “a wrinkle on the face:)
  • Small Intestine: plicae circulares
  • Large Intestine: haustra (Latin haurere: “to draw up”)
120
Q

Mechanical Digestion in Organs

A

Oral Cavity:

  • chew food, tongue and cheeks move food
  • swallowing mixes food

Esophagus:
- peristalsis mixes food

Stomach:

  • contractions of stomach mix food
  • rugae help in mixing

Small Intestine:

  • peristalsis mixes food
  • plicae circulares aid in mixing

Large Intestine:

  • peristalsis mixes food
  • haustra aid in mixing
121
Q

Chemical Digestion in Organs

A

Oral Cavity:
- salivary glands secrete enzymes that break down starches and fats

Stomach:

  • hydrochloric acid breaks down foods
  • pepsin breaks down proteins
  • gastric lipase breaks down fats

Small Intestine:

  • pancreas releases bicarbonate to neutralize acid + enzymes to break down food
  • bile salts from liver emulsify fats

Large Intestine:
- beneficial bacteria make vitamin K, digest cellulose (fiber), and make methane.

122
Q

What are the 9 Enzymes found in the Small Intestinal Brush Border?

A

In the small intestine, enzymes which carry out chemical digestion are found along the brush border. Look brushy because microvilli are coated with proteins (enzymes), giving them a fuzzy appearance. The 9 enzymes of the brush border are:

  • alpha-dextrinase
  • maltase
  • sucrase
  • lactase
  • enterokinase
  • aminopeptidase
  • dipeptidase
  • nucleosidases
  • phosphatases
123
Q

What Enzyme is Secreted by the Salivary Glands?

A

Salivary amylase: found in starches

124
Q

What 2 Enzymes are Secreted by the Stomach?

A
  • Pepsin: found in proteins

- Lipase: found in triglycerides (fats and oils)

125
Q

What 5 Enzymes are Secreted by the Pancreas?

A
  • Amylase: found in starches
  • Trypsin, Chymotrypsin, & Elastase: found in proteins
  • Carboxypeptidase: found in amino acid at carboxyl end of proteins
126
Q

What 9 Enzymes are Found in the Small Intestinal Brush Border?

A
  • Maltase, Sucrase, Lactase: found in maltose, sucrose, lactose
  • Amino peptidase: amino acid at amino end of proteins
  • Nucleosidases & Phosphateses: found in nucleotides
127
Q

Colloids

A

In a colloid, dispersed solid particles are larger than in a solution - large enough to scatter light

Particles in a colloid stay dispersed over time

128
Q

Suspensions

A

A suspension has even larger particles than a colloid, and these settle to the bottom of a container given time - like muddy water.
- Blood is a suspension, a colloid, and a solution. Red blood cells are suspended in plasma, plasma is a colloid of large proteins dispersed in a solution of sodium chloride and other salts.

129
Q

Emulsion

A

An emulsion is a colloid where all components are liquid.
- Milk is an emulsion and a solution: large proteins and fat droplets are in a liquid colloidal suspension (emulsion); sugars are dissolved in solution.

130
Q

Chyme

A

The mixture of nutrients and GI secretions called chyme is an emulsion, so chyme is an example of an emulsion.
- In order for enzymes to act on chemicals in food, the digestive system must emulsify chyme with digestive juices. (e.g. fats are insoluble in water; bile salts emulsify fats so that lipases can act on them)

When lipid is emulsified in a water-based solution, the particles are called micelles.

Anatomy and Physiology 1111 (7 decks)

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