Lecture Exam 1 -- Chapter 24 Study Guide Flashcards Preview

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Flashcards in Lecture Exam 1 -- Chapter 24 Study Guide Deck (45):
1

COMPONENTS OF THE GI TRACT --
Know the anatomy and functions: Mouth

Lies between teeth, hard palate, soft palate
and tongue.

During swallowing soft palate and uvula
draw together to prevent food from entering the nasal cavity.

2

COMPONENTS OF THE GI TRACT --
Know the anatomy and functions: Pharynx

Involved in deglutition (swallowing or movement of food from mouth to stomach).

3

COMPONENTS OF THE GI TRACT --
Know the anatomy and functions: Esophagus

Involved in deglutition (swallowing or movement of food from mouth to stomach).

Muscle changes from skeletal to smooth from the superior to inferior end of espohagus.

Upper esophageal sphincter - skeletal muscle

Lower esophageal sphincter - smooth muscle

Epithelium - non-keratinized stratified squamous

4

COMPONENTS OF THE GI TRACT --
Know the anatomy and functions: Stomach

J-shaped organ.

Entry controlled by lower esophageal
sphincter.

Exit controlled by pyloric sphincter.

Stomach is a mixing chamber and a
reservoir.

It takes 2-4 hrs for food entering stomach
after a meal to leave.

Functions:
1) Makes chyme - mixture of saliva, food and gastric juices.
2) Holds food until room in small intestine
3) Secretes acid (HCl) - this kills bacteria and denatures protein.
4) Secretes pepsin - an enzyme that starts breaking down protein.
5) Secretes intrinsic factor - aides in Vit B 12 absorption.
6) Secretes lipase - starts digestion of fats
7) Secretes gastrin - a hormone.

5

COMPONENTS OF THE GI TRACT --
Know the anatomy and functions: Small Intestine

Duodenum - closest to stomach
Jejunum
Ileum - closest to large intestine
Mucosa specialized for absorption as well
as secretion.

6

COMPONENTS OF THE GI TRACT --
Know the anatomy and functions: Large Intestine

Opening from ileum of small intestine to
large intestine guarded by ileocecal
sphincter.

Materials pass from the cecum to the colon
to the rectum to the anus.

Functions of the Large Intestine:
1) Completion of absorption particularly water
2) Production of some B vitamins and vitamin K
3) Formation of feces
4) Expulsion of feces
Movement through large intestine achieved by haustral churning (formation of pouches by movement of muscle bands in the muscularis)

7

ACCESSORY DIGESTIVE ORGANS --
Name the Accessory Digestive Organs.

Teeth, tongue, salivary glands, liver, pancreas, gall bladder.

Understand that these organs are classified as part of the digestive system since, although most do not come into contact with food, their major functions are to secrete or store secretions needed for digestion.

8

FUNCTIONS OF THE GI SYSTEM --
Know the major functions of the digestive system.

1) Ingestion - eating

2) Secretion of substances to aide in digestion - water, acid, buffers, enzymes.

3) Mixing and propulsion- achieved by smooth muscle walls to move food along - called gut motility.

4) Digestion
- mechanical - teeth for grinding, smooth muscle for churning
- chemical - large molecules converted into smaller molecules by digestive enzymes
- the digestive enzymes are produced by the tongue, stomach, pancreas and small intestine. Role of enzymes is to catalyze chemical reactions.

5) Absorption - term refers to process of
digested food, fluids and ions crossing the gut wall to enter blood or lymph. Selective
absorption facilitated by properties of
epithelial cells.

6) Defecation - disposal of wastes.

9

LAYERS OF THE GI TRACT --
What layers are present?
What type of epithelium is present in each location?

Same basic 4 layers through-out GI tract with
some variation dependent on function at
specific location.

1) Mucosa (inner lining) - consist of an
epithelium, CT layer called the lamina
propria and a thin layer of smooth muscle.
2) Submucosa - areolar CT.
3) Muscularis
4) Serosa- serous membrane

In the mouth, pharynx, esophagus and anal
canal epithelium is non-keratinized
stratified squamous - provides protection.

In the stomach and intestines epithelium is
simple columnar - provides selective
surface for secretion and absorption.

10

LAYERS OF THE GI TRACT --
What layers are present?
How do the structures of these layers vary in different locations?
How is structure related to function?

Same basic 4 layers through-out GI tract with
some variation dependent on function at
specific location.

1) Mucosa (inner lining) - consist of an
epithelium, CT layer called the lamina
propria and a thin layer of smooth muscle which makes the mucosa fold - increases surface area for absorption.

2) Submucosa - Areolar CT with many neurons (part of enteric nervous system).

3) Muscularis -

4) Serosa- Outer layer of GI wall. Consists of areolar CT and a simple squamous epithelium
often called mesothelium.

11

LAYERS OF THE GI TRACT --
What is MALT and where is it located?

Lamina Propria contains immune cells in clusters called mucosa-associated lymphatic tissue (MALT).

Most MALT found in tonsils, small
intestines, appendix and large intestine.

12

NEURAL INNERVATION OF THE GI TRACT --
Where are the two plexuses of the GI tract located?
What are they called?
Do they interconnect?
What are their respective functions?

Arranged in 2 plexuses:

Myenteric plexus (plexus of Auerbach) -
located between circular and longitudinal
muscle layers of muscularis. Myenteric plexus controls gut motility.

Submucosal plexus (plexus of Meissner) -
located in submucosa. Submucosal plexus controls secretion

The 2 plexuses are interconnected by interneurons.

13

NEURAL INNERVATION OF THE GI TRACT --
What is the role of the autonomic nervous system in the gut?
Where do the autonomic nerves arise?

In general:
Parasympathetic nerves increase GI secretion and motility
Sympathetic nerves decrease GI secretion and motility.

Most parasympathetic nerves enter GI via
cranial nerve X (vagus) - except large
intestine which is supplied by
parasympathetic fibers from sacral spinal
cord.

Sympathetic nerves supplying gut arise
from thoracic and lumbar regions of spinal
cord.

14

PERITONEUM --
Where is the peritoneal cavity? Where are the different layers?

The peritoneum is the largest serous membrane in the body. there are two layers of the peritoneum, with the parietal peritoneum lining the inner surface of the abdominopelvic wall and the visceral peritoneum covering organs within the abdominopelvic cavity. Secures organs together and to the abdominal wall.

15

PERITONEUM --
What is the name of the fluid in the peritoneal cavity?

peritoneal fluid, which consists of water, electrolytes, leukocytes and antibodies.

The fluid serves two main functions:
- It acts as a lubricant, enabling free movement of the abdominal viscera.
= The antibodies fight infection.

16

PERITONEUM --
What is peritonitis?

Peritonitis refers to infection and inflammation of the peritoneum

17

PERITONEUM --
What is ascites fluid?

Ascites refers to an accumulation of excess fluid in the peritoneal cavity. It can occur in conjunction with infection and peritonitis,

18

SALIVARY GLANDS --
Know where the major salivary glands are located.

1) Parotid glands - anterior and inferior to the ears between the skin and the masseter muscle.

2) Submandibular glands - in the posterior part of the mouth floor just medial to the madnible, deep to the mylohyoid muscle.

3) Sublingual glands - under the tongue.

19

SALIVARY GLANDS --
What is present in saliva?

Enzymes that intiate chemical digestion of carbohydrates and lipids.

20

SALIVARY GLANDS --
What is the condition called “mumps”?

The paramyxovirus targets the parotid glands which become inflamed and enlarged (commonly called mumps).

Vaccination became available in 1967.

Very painful. Also causes inflammation of testes in adult men.

21

PHARYNX AND ESOPHAGUS --
What is gastrointestinal reflux disease?

If lower esophageal sphincter does not close completely stomach contents can back-up
(reflux).

Stomach contents highly acidic (contain HCl).

Acid irritates esophageal wall - often called heartburn.

Untreated can lead to esophageal cancer.

22

STOMACH --
Know the anatomy and histology of the stomach, including the names of each cell type and the types of secretions they produce.

Columnar epithelium of mucosal layer of wall forms
columns of secretory cells called gastric glands.

3 types of exocrine cells:
1) Mucous neck cells - secrete mucous
2) Parietal cells - secrete HCl and intrinsic factor.
3) Chief cells - secrete pepsinogen and gastric lipase.

One type of endocrine cell - G cells - secrete gastrin.

23

STOMACH --
Know the functions of the stomach.

1) Makes chyme - mixture of saliva, food and gastric juices.

2) Holds food until room in small intestine

3) Secretes acid (HCl) - this kills bacteria and denatures protein.

4) Secretes pepsin - an enzyme that starts breaking down protein.

5) Secretes intrinsic factor - aides in Vit B 12 absorption.

6) Secretes lipase - starts digestion of fats

7) Secretes gastrin - a hormone.

24

STOMACH --
Know which glands are classified as exocrine and which are classified as endocrine.

EXOCRINE:
1) Mucous neck cells - secrete mucous
2) Parietal cells - secrete HCl and intrinsic factor.
3) Chief cells - secrete pepsinogen and gastric
lipase.

ENDOCRINE: G cells - secrete gastrin

25

STOMACH --
Know the mechanisms of secretion of HCl by parietal cells.

Hydrogen and Chloride ions enter lumen of stomach by specialized transport processes.

1) Proton pumps using energy from H+/K+ ATPases actively transport H+ ions into lumen in exchange for K+ ions.

2) Chloride ions enter via membrane channels.

HCl secretion increased by:
= Acetylcholine from parasympathetic neurons
Gastrin from G cells
= Histamine from mast cells: Histamine acts synergistically on ACh and Gastrin

The hydrogen ion concentration in parietal cell secretions is roughly 3 million fold higher than in blood, and chloride is secreted against both a concentration and electric gradient. Thus, the ability of the partietal cell to secrete acid is dependent on active transport.

The key player in acid secretion is a H+/K+ ATPase or "proton pump" located in the cannalicular membrane. This ATPase is magnesium-dependent, and not inhibitable by ouabain. The current model for explaining acid secretion is as follows:

Hydrogen ions are generated within the parietal cell from dissociation of water. The hydroxyl ions formed in this process rapidly combine with carbon dioxide to form bicarbonate ion, a reaction cataylzed by carbonic anhydrase.
Bicarbonate is transported out of the basolateral membrane in exchange for chloride. The outflow of bicarbonate into blood results in a slight elevation of blood pH known as the "alkaline tide". This process serves to maintain intracellular pH in the parietal cell.
Chloride and potassium ions are transported into the lumen of the cannaliculus by conductance channels, and such is necessary for secretion of acid.
Hydrogen ion is pumped out of the cell, into the lumen, in exchange for potassium through the action of the proton pump; potassium is thus effectively recycled.
Accumulation of osmotically-active hydrogen ion in the cannaliculus generates an osmotic gradient across the membrane that results in outward diffusion of water - the resulting gastric juice is 155 mM HCl and 15 mM KCl with a small amount of NaCl.

26

STOMACH (Use Table 24.3 as a useful summary.)--
What factors regulate HCl secretion from the stomach?

HCl secretion increased by:
Acetylcholine from parasympathetic neurons
Gastrin from G cells
Histamine from mast cells.
Histamine acts synergistically on ACh and Gastrin

27

PANCREAS --
What portion of the pancreas is endocrine and what portion is exocrine?

99% exocrine acini
1% clusters of endocrine cells called Islets of
Langerhans- secrete hormones (insulin, glucagon,
somatostatin and pancreatic polypeptide).

28

PANCREAS --
What enzymes are produced by the exocrine portion of the pancreas?
What do these enzymes do?

Amylase - digests starch (complex
carbohydrates).

Trypsin, chymotrypsin, carboxypeptidase,
elastase - digest proteins.

Lipases - digest fats.

Ribonucleases and Deoxyribonucleases digest
nucleic acids.

29

PANCREAS --
What hormones are produced by the endocrine portion of the pancreas? - (these will be studied in more detail when we cover endocrinology).

1% clusters of endocrine cells called Islets of
Langerhans- secrete hormones (insulin, glucagon,
somatostatin and pancreatic polypeptide).

30

LIVER & GALL BLADDER --
How is a liver lobule arranged? What is a portal triad?

Organized into lobules around a central vein.
Portal Triad: hepatic portal vein, hepatic artery, bile duct branch.

31

LIVER & GALL BLADDER --
Which way does the blood flow in a liver lobule?

inward, toward the central vein.

32

LIVER & GALL BLADDER --
What cell-types are present in a liver lobule and what do they do?

2 types of epithelial cells - hepatocytes and bile
duct cells.
Also phagocytic cells called Kupffer cells.

33

LIVER & GALL BLADDER --
What are the major functions of the liver?

1) Carbohydrate, lipid and protein metabolism.
2) Processing of drugs and hormones.
3) Excretion of bilirubin.
4) Synthesis of bile salts.
5) Storage of vitamins and minerals.
6) Phagocytosis (via Kupffer cells).
7) Activation of Vitamin D.

34

LIVER & GALL BLADDER --
What is the location and function of the gallbladder?

Pear shaped sac in depression in liver.
Stores and concentrates bile.

35

LIVER & GALL BLADDER --
Where is bile produced and what does it do?

Secreted by hepatocytes. Stored by gall bladder.

Aged blood cells destroyed and generate iron, globin and bilirubin.

Bilirubin gives bile a greenish color.

Bilirubin excreted

Bile salts involved in breakdown of large lipids
via process called emulsification.

36

SMALL INTESTINE --
Name the different components of the small intestine.

Duodenum - closest to stomach
Jejunum
Ileum - closest to large intestine

37

SMALL INTESTINE --
What is the brushborder and how does it function?

Microvillus border of intestinal epithelial cells is referred to as the "brush border". Mucosa specialized for absorption as well as secretion.

38

SMALL INTESTINE --
What enzymes are responsible for carbohydrate digestions? Where are they located?

Initially digested by salivary and pancreatic
amylase.

Further digested by enzymes from the brush border
of the small intestine:
α-dextrase
sucrase
lactase
maltase

39

SMALL INTESTINE --
What enzymes are responsible for protein digestion?

Starts in stomach by action of pepsin.

Continues by action of pancreatic trypsin, chymotrypsin, carboxypeptidase and elastase.

Completed by peptidases of brush border (aminopeptidase and dipeptidase).

40

SMALL INTESTINE --
What enzymes are responsible for nucleic acid digestion?

Pancreatic juice contains ribonucleases and deoxribonucleases.

Brush border enzymes, nucleosidases and phosphatases further digest nucleic acids into pentose sugars, phosphates and nitrogenous bases that are small enough for absorption by active transport.

41

SMALL INTESTINE --
What are the end-products of carbohydrate, protein and lipid digestion?

Carbohydrates are converted to monosaccharides (glucose, fructose, galactose).

Proteins are converted to amino acids (and some di- and tripeptides).

Lipids are converted to fatty acids and glycerol.

42

SMALL INTESTINE --
How are sugars and amino acids absorbed?

Secondary active transport, facilitated diffusion and active transport used to move simple sugars and amino acids across gut wall and into blood.

Molecules need to move from lumen of gut across apical membrane and then from cell across basolateral membrane

43

SMALL INTESTINE --
How are lipids absorbed? Note the differences between different types of lipids.

Short chain fatty acids can be absorbed by simple diffusion.

Long chain fatty acids and monoglycerides form
tiny spheres called micelles by interacting with bile salts.

Once transported to the brush border the long chain fatty acids and monoglycerides are released from the micelles and enter the cell.

Inside the cell they form large aggregates called
chylomicrons.

The chylomicrons leave the cell by exocytosis.
Chylomicrons are too large to enter capillaries so are transported via the lacteals of the lymphatic system.

44

FLUID BALANCE IN THE GI TRACT --
What fluids contribute to the process of digestion?

It takes a lot of fluid to process food.
Most of the fluid is reabsorbed in the small
intestine.

45

LARGE INTESTINE --
Know the anatomy of the large intestine.
What are the functions of the large intestine?

Opening from ileum of small intestine to large intestine guarded by ileocecal sphincter.

Materials pass from the cecum to the colon to the rectum to the anus.

1) Completion of absorption particularly water
2) Production of some B vitamins and vitamin K
3) Formation of feces
4) Expulsion of feces

Movement through large intestine achieved by haustral churning (formation of pouches by movement of muscle bands in the muscularis)