Flashcards in Lecture 41 - Principles of viscera Deck (43):
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?
What is the inside of a hollow viscera called?
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...
1. Expansion to store large quantities (eg, bladder);
2. Motility (eg, peristalsis of the small intestines)
3. 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.
1. Cortex (outer) and medulla (inner) (eg, kidneys);
2. 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?
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.
Give an example of an anatomical sphincter that has a ring of skeletal muscle. Why would an anatomical sphincter have skeletal muscle?
Urethra or rectum. Skeletal muscle gives us voluntary control over the passage of contents out of those tubes and so it acts as a "2nd line of defense" for control of excretion/defecation.
What is the serous membrane?
A thin, smooth membrane of cells that secrete serous fluid and surround the cavities of the abdomen and thorax.
What are the two structural subdivisions of the serous membrane?
Peritoenum (covers the walls of the body cavity) and visceral (covers the viscera)
What are the two structural subdivisions of the visceral serous membrane?
Parietal - abdominal cavity
Pleural - Thoracic cavity
With what structure does the parietal serous membrane share its nerve and blood supply?
It shares the nerve and blood supply of the thoracic/abdominal walls.
With what structure does the visceral serous membrane share its nerve and blood supply?
It shares the nerve and blood supply of the viscera that it surrounds.
Are the parietal and visceral layers of serous membrane structurally separate?
No; they are a single continuous membrane.
How does the serous membrane assist the nerves and vessels of the viscera?
The serous membrane wraps around to form a pathway for nerves, arteries, and veins to move from posterior wall of the cavity to the viscera.
What is a mesentery?
Fold of peritoneum that suspends viscera in the body cavity.
What are the two roles of mesentery?
1. Provide a pathway for nerves and vessels to the viscera.
2. Provide viscera with mobility within the body cavity (eg, for stomach expansion.)
Viscera suspended in mesentery are at risk of what injury? What is the most serious consequence of this injury? Give an example of a viscera that is at risk.
Structures within the mesentery are in danger of torsion/twisting. Torsion may block blood supply and cause avascular necrosis. An example of this if twisting of the testes.
What is referred pain?
Pain experienced at a site different from its source, usually referred to the skin.
What developmental reasons cause referral of pain?
Referred pain arises because somatic structures and visceral structures share the same spinal cord segment but they migrate away from each other during development .
Give an example of referred pain.
During a heart attack the sufferer may feel pain in the dermatome of their left upper arm.
Give an example of paired viscera. Do a set of paired viscera share the same blood supply?
Kidneys, adrenals, testes, lungs. Each of a set of paired viscera have separate blood supply.
True or false: referred pain from paired viscera occurs on both sides of the body because they share the same nerve supply, despite sharing the same blood supply.
False; referred pain from paired viscera occurs on the side of the body that is injured because each of a set of paired viscera has its own distinct nerve supply.
True or false: unpaired viscera develop along the midline.
Where do unpaired viscera refer pain to? Can this change? Why?
The midline, even if the pathology is not at midline. Yes, pain may only shift if the overlying peritoneum is affected by the inflammation. The overlying peritoneum shares the same nerve supply as the overlying skin.