Lecture 41 - Principles of viscera Flashcards
What are the two types of viscera?
Hollow/tubular and solid viscera
What are the 4 activities in which viscera are involved?
SEDA - secretion, excretion, digestion, absorption
What is the role of all viscera?
To regulate the body’s internal environment.
Most organ systems do not include which anatomical region?
The back.
What is the inside of a hollow viscera called?
The lumen
What are the three layers of hollow viscera?
External - serosa.
Intermediate - muscularis.
Internal - mucosa.
What two structural features increase the internal surface area of hollow viscera?
Folds in the mucosa and/or villi on mucosa
Where are hollow viscera most likely to have constrictions?
At the beginning and end of the tube.
Other than functional and anatomical sphincters, what might cause constrictions in hollow viscera?
Constrictions can be caused by adjacent structures. Eg, the aortic arch compressing the esophagus or the pelvic brim constricting the ureters.
Why is it clinically important to know where constrictions are in hollow viscera?
Constrictions are the most likely place that objects will become lodged in hollow viscera, eg calculuses passing from the kidney to the bladder are most likely lodged in an orifice or at the pelvic brim.
If you were a doctor, how could you detect an obstruction in a patient’s ureter?
Ingestion of a radioactive dye that is passed in the urine. Upon x-ray the lye will stop or thin out at any restrictions in the ureters.
What two subtypes of smooth muscle make up the walls of hollow viscera?
Circular and longitunidal
What are the 3 benefits of having smooth muscle in the walls of hollow viscera? Give a specific example of each benefit.
It allows for…
- Expansion to store large quantities (eg, bladder);
- Motility (eg, peristalsis of the small intestines)
- Smooth muscle can be stretched without loosing tension, thus it can contract with enough force to push contents to the exterior (eg, during urination.)
Solid viscera are organized into clusters of cells. What are the two way in which hollow viscera may be structurally organized? Give an example of each.
Into either…
- Cortex (outer) and medulla (inner) (eg, kidneys);
- Lobes and lobules (eg, lungs)
Are lobes of solid viscera divided functionally or structurally?
Trick question: lobes of solid viscera can be divided functionally or structurally.
Solid viscera have an external capsule, the ‘serosa.’ What is its role?
Reduce friction.
How do adjacent structures affect solid viscera? Give an example.
Solid viscera tend to have impressions/marks from adjacent structures. Eg, left lung has the cardiac impression: the heart and the aortic arch.
What are the two types of sphincters of tubular viscera?
Anatomical and functional
What are the two main roles of sphincters?
Control passage of contents into the next section and to stop reflux of contents.
Describe the structure of an anatomical sphincter. How does this structure control the passage of contents?
Ring of muscle. When the muscle is contracted it ‘strangles’ the tube closed.
What happens if you change the tone of a smooth muscle? Give an example.
Anything that alters tension/tone of smooth muscle can cause unchecked flow of contents. Eg, caused by cancer or nerve damage or drugs.
Describe the structure of an fuctional sphincter using an example from the lecture. How does this structure control reflux of contents back into the tube?
The ureter enters the muscular wall of the bladder obliquely. Thus, when the bladder contracts during urination it also closes the end of the ureter, and therefore stops reflux. (See slide 12 for illustration.)
What is the key difference between anatomical and functional sphincters?
Functional sphincters have no localized muscle thickening.
True or false: anatomical sphincters are only ever made of smooth muscle.
False: Anatomical sphincters may have both rings of skeletal muscle and rings of smooth muscle.
