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.

Objectives 63 & 66: Renal corpuslces and tubules and tasks of the nephrons

Describing the structure and function of the renal corpuscles and tubules and identifying the three basic tasks performed by the nephrons and tubules.....

Picture from Anatomy and Physiology textbook*

I have to say, I've really enjoyed this textbook.  Its been really easy to read and follow along with compared to some of the science texts that I've used in other classes.  The fact that the text and picture are both color coordinated to show the three processes that the nephrons perform and where it occurs in the renal corpuscle and tubules was a geat starting place in understanding these objectives. Breaking the processes down like this makes them seem less overwhelming.

Objectives 52, 65, & 69: Blood pressure and volume, juxtoglomerular cells and renin, and water excess and dehydration

Detailing the kidneys involvement in blood pressure and volume regulation, stating the importance of the juxtoglomerular cells in secretion of renin, and assessing how water excess and dehydration affect kidney function.....

Understanding how the kidneys work to maintain blood volume and blood pressure is tricky because there are multiple methods (and hormones) that can be involved in doing this. I had a good understanding of the hormones that were involved including aldosterone and ADH, but was a little bit iffy on where renin fit into the process.  Watching this video where they gave a step by step explanation of how the release of each hormone causes a cascade effect onto another organ helped me to get a better grasp of the entire process. 

In all of the processes listed above there is one additional factor that plays a large part in maintaining body homeostasis and that is WATER!  So its important to discuss and understand how water excess or dehydration ties into maintaining blood volume and blood pressure as well.  When the body becomes dehydrated due to excessive fluid loss or a decrease in fluid intake  the extracellular fluid becomes a hypertonic solution for the cells.  This means that the water in the cells will move out into the extracellular fluid (following those salts or solutes like water always does!) causing the cell to crenate.  On the other hand, when we have excessive amounts of fluid in the system, the cells are in a hypotonic solution.  So the water in the extracellular fluid will move into the cells causing them to overfill and lyse. 

Nurse's Note: Diuretics are commonly prescribed along with antihypertensive medications to treat high blood pressure.  Just another example of how blood pressure and blood volume tie in together.