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Digestive System (The Small Intestine and its functions: (Circular Folds:…
Digestive System
The Small Intestine and its functions:
Circular Folds
: They slow down the chyme in the small intestine.
Villi:
They look like fingers, they increase surface area.
Functions
: Mechanical digestion: Segmentation
Chemical digestion: Lots of enzymes are added here. Lots of absorption.
Microvilli / Brush border
: These structures are on each of the villi, and they further increase surface area.
Duodenal glands:
These glands secrete alkaline mucus to neutralize acid from the stomach. It provides the small intestine with protection against its own powerful chemicals.
Peyer Patches (Lymphatic nodules)
:
Collections of lymphocytes are what make up the lymphatic nodules.
Intestinal Glands:
These glands secrete watery intestinal juices to keep things in a constant liquid state.
The function of the
ileocecal valve
is that It keeps the contents in the large intestine there; and not moving backward to the small intestine.
The Stomach and its functions:
Gastric Glands:
The Gastric Glands continue from the Gastric Pits that are in the General Layer (Mucosa) of the stomach. Gastric glands make up the cardiac sphincter and the pyloric sphincter, as well as located in the body and the fundus of the stomach. Depending on their location, they are made up of different types of cells. The Mucous neck cells are located in the neck of the gastric glands.
Parietal Cells
(Oxyntic): (middle region of the gastric glands) Produces hydrochloric acid (HCl) and intrinsic factor. Intrinsic factor is needed for the absorption of vitamin B12. Vitamin B12 is needed for erythrocytes production.
-Food Storage -Mechanical digestion and churning. This turns food into chyme -Chemical digestion
Chief cells/Chief glands
: (mainly in the basal part of the gastric glands) Makes and secretes pepsinogen. Pepsinogen + acid = pepsin. Pepsin is an enzyme that breaks down proteins/fats. (gastric lipase).
The
cardiac sphincter
prevents the reflux of acid into the esophagus. It is weaker than the pyloric sphincter. (heartburn is the acid in the esophagus that leaked through a weak cardiac sphincter).
The
pyloric sphincter
regulates the amount of chyme moving on to the small intestine. It moves on to the small intestine slowly (the stomach is a holding place for food until it’s ready to be moved to the small intestine).
The
rugae
in the stomach increases the storage capacity.
Mesentery and its function:
2.) Stores Fat
3.) Provides a place for blood vessels and nerves to go
1.) It holds organs in place
Mesentery:
This is a double layer of peritoneum from the body wall to digestive organs.
Compare and contrast the locations of the mesenteries:
(mesentery proper, mesocolon, lesser omentum and greater omentum)
The
Mesocolon
: This is connected to the transverse colon and the sigmoid colon on the posterior side.
Lesser Omentum:
This starts at the lesser curvature of the stomach and it goes to the liver.
The
Mesentery Proper
is located within the jejunum and the ileum of the Small Intestine.
Greater Omentum:
This can migrate. (Example: if the appendix is infected, the greater omentum can migrate to that area, through natural movements from the body.) The Greater Omentum can cover the infected organ, thereby protecting all of the surrounding tissue. The greater omentum is also used for fat storage.
Large Intestines, Rectum and Anal Canal
general functions:
Large Intestine
: Absorption of water and electrolytes (ions)
Rectum:
Storage place. There are well developed muscles to expel feces.
Anal Canal
: Last inch or so of the large intestine.
There are mucus glands located here for lubrication. Internal (Smooth Muscles/Involuntary) Sphincters
and External (Skeletal Muscles/Voluntary) Sphincters.
Teniae Coli:
Three longitudinal strips of muscle. They contract and pull the large intestine into pouches / sacks.
Haustra
: These are the pouches / sacks.
Epiploic Appendages
: Little pieces of fat on our large intestine
Function of the Liver, Gallbladder and Pancreatic Acini
Gallbladder
:The gallbladder stores bile (made by the liver)
Pancreatic acini
The Pancreatic acini are cells that make up the bulk of the pancreas. They are exocrine glands that produce and secrete 22+ enzymes that enter the duodenum.
Liver
:
-The Lives makes bile (which is stored in the gallbladder).
The bile emulsifies fat (breaking it into smaller pieces)
-Filters toxins out of the blood
-Stores glucose (sugar) as glycogen
-Stores some vitamins
-Processes fats and amino acids
-Makes blood proteins
Major functions of the digestive system:
Break down food into small enough pieces to be absorbed (To eventually go into the circulatory system – blood)
Eliminate what we can’t break down.
Gastrointestinal (GI) Tract / Alimentary canal and the accessory digestive organs:
The GI is the tube. It starts at the mouth and ends at the anus. Again, the GI Tract is simply a tube. The organs of the GI Tract include: The mouth, Pharynx, Esophagus, Stomach, Small Intestine, Large Intestine, and anus.
The accessory digestive organs are organs we find along the tube. These include: The teeth, tongue, gallbladder, salivary glands, liver and pancreas. The Accessory organs secrete saliva, bile and enzymes to aid in breaking down the foodstuff.
Mechanical Digestion and Chemical Digestion
Mechanical Digestion is cutting up food to make it into smaller pieces.
Mechanical Digestion:
The teeth start the mechanical process, Stomach, Small Intestine (A movement in the small intestine, called segmentation occurs). This is all part of MECHANICAL DIGESTION.
Chemical Digestion is when chemicals (Specifically enzymes) are added.
Chemical Digestion:
It starts in the mouth with saliva (Chemicals from the Pancreas), Stomach (More chemical added), Small intestine.
Intraperitoneal and Retroperitoneal Organs:
Intraperitoneal organs
are those within the peritoneal. The digestive system organs that are located here include: Liver, Stomach, Transverse Colon, Jejunum, Ileum and the Sigmoid Colon.
Retroperitoneal organs
are those outside the peritoneal. The digestive system organs that are located outside the peritoneal include the: Duodenum, Pancreas, Ascending Colon, Descending Colon and Rectum.
Peristalsis
Peristalsis
is a movement of continual contraction, and than a period of rest in the musculature of the organ wall. Its next effect is to squeeze food from one organ to the next. It’s the esophagus through the large intestine.
Pathway that food travels as it enters the oral cavity and leaves the anus:
Oral Cavity :check: Pharynx :check: Esophagus :check: Stomach :check: Small Intestine (Has three parts) :check: Large Intestine :check: Rectus :check: Anus
Portal Circulation
:
Heart 2. Arteries (Digestive System) 3. Capillaries 4. Veins (Hepatic Portal Vein) 5. Capillaries (of the liver) 6. Veins (Hepatic Portal Vein and Inferior Vena Cava) 6. Back to the heart