Objective 78: The Alimentary Canal

Distinguish among the different parts (gross and histological) of the alimentary canal in terms of structure and function.................

This picture from the Anatomy and Physiology textbook* explains the basic layers of all portions of the alimentary canal.  One of the greatest hurdles to overcome with the alimentary canal is the understanding that while all layers have an internal epithelium for the mucosa, each of those layers will have a different type of epithelium that relates to the structures function.  For example the mouth and esophagus have an epithelium layer of stratified squamous to protect them from abrasion.  The stomach and the small intestine are both lined with simple columnar epithelium yet the stomach epithelium is designed for secretion of gastric juices while the small intestines epithelium is designed for absorption.

Nurse's Note: Damage to the stomach's epithelial lining can lead to gastric ulcers which can cause severe stomach pain.  Once thought to be caused by certain medications and ingesting spicey food, the H.Pylori bacteria is now thought to be the most common cause.

Objective 57: Lacteals

Justify the role of lacteals in transporting products of digestion..............

A lacteal is a lymphatic capillary that absorbs dietary fats in the villi of the small intestine. http://en.wikipedia.org/wiki/Lacteal


http://en.wikipedia.org/wiki/Lacteal

I'm really not sure how to reflect on this except to say that it seems pretty basic.  The villi in the small intestine contain both a lacteal or lymph capillary and a capilary bed.  The digested food is absorbed into the epithelium and sent throughout the body via the lymph capillary and the capillary bed. 

Also, this lacteal picture reminds me of a sunflower !  



Objective 59: Microscopic Anatomy of the Liver

Appreciate the microscopic anatomy of the liver.....


Liver



Understanding that the livers overall function in the body is to filter and process the blood supply helps with understanding the microscopic anatomy.  The photo that I took in lab helps me in grasping the concept that the liver lobules are a six-sided shape with a central vein running through it.  The picture from the Anatomy and Physiology text* shows in depth what occurs at the portal triad on each one of those corners.  Reading through the text explained the many facets of the liver including:

Glycogen storage

Decomposition of RBC'S

Plasma protein synthesis

Hormone production and detoxification

Bile production

Nurse's Note: Two common diagnoses that pertain to the liver are Hepatitis, a long-term, chromic and potentially fatal infection of the liver caused by a virus and Cirrhosis, a chronic infection of the liver caused by alcoholism. 

Objective 58: Hormones and Digestion

Relay structure and function of the endocrine system to digestion...........

These two pictures from the Anatomy and Physiology textbook*  along with time in both lab discovery and lecture gave a full understanding of the role that the endocrine system plays in digestion.  The pancreas is labeled as both and endocrine and exocrine gland.  Its exocrine functions include the release of enzymes that aid in digestion and its endocrine functions include the release of both insulin by the beta cells and glucacon by the alpha cells.  These two secretions work antagonistically to one another to maintain the proper amount of glucose in both the blood and the cells.

 I had an "AHA" moment while listening to one of the podcasts regarding glucagon and insulin.  It was so "AHA" and had me so turned around that I actually had to get Jeremy to explain it to me again!  While listening to the podcasts on the endocrine system the question was posed "What would be the result of too much insulin in the blood stream"?  I know the answer to this, I thought!  High blood sugar!  WRONG, so WRONG!  The answer was hypoglycemia.  What?  How can that be?  I was so perplexed that I actually had to grab Jeremy in the parking lot at school, make him listen to that section of the podcast and then pretty much force him to repeatedly explain it to me.  He laughed as he explained that I apparently had the functions of insulin and glucagon backwards.  Insulin actually moves the glucose into the cell while glucagon breaks down glycogen from the liver and puts glucose back into the blood stream. 

Thank you, Jeremy for setting me straight!

Nurse's Note: Diabetes Mellitus occurs when there is too little insulin in the blood and glucose can not be effectively moved into the cells.  There are three cardinal signs of Diabetes Mellitus.  These include polyuria or excessive urine output, polydipsia or excessive thirst, and polyphagia or excessive hunger.

Objectives 60 & 61: Chemical forms that major food classes are absorbed and pancreatic juices

State the chemical forms in which the major food classes are absorbed and describing enzymatic and bicarbonate content of pancreatic juices.

This sheet from the Anatomy and Physiology Laboratory Manual** gave a thorough description of how the major food classes were broken down into chemical forms for absorption.  In addition to the chart shown here, lab exercises were done to increase understanding of how the foods were broken down and what organs played a mjor part in making that happen.  In addition, the chart also highlights the pancreatic enzymes that play a part in digestion of these food sources such as pancreatic amylase that works to breakdown carbohydrates, Trypsin that works to break down proteins, pancreatic lipase that works on fats, and pancreatic ribonuclease and deoxyribnuclease that breakdown amino acids.  All of these enzymes are secreted from the pancreas in an inactive form and are activated in the small intestine.

Nurse's Note: Carbohydrates, proteins, and fats are considered macronutrients because our body requries these food sources in large amounts in order to function properly.  Carbohydrates are the body's major source of energy and the only source that the central nervous system can use.  Proteins fuel and build muscle while fat offers additional energy and protection of the organs.