Lecture 41 - Principles of Viscera Flashcards
What is the general overarching function of viscera?
To regulate the internal environment
Which four processes are the viscera involved with?
Secretion
Absorption
Excretion
Digestion
What are the two types of viscera?
Solid
Tubular (hollow)
Give some examples of hollow organs
Trachea Bronchi Oesophagus Stomach Intestines
Give some examples of solid organs
Liver
Lungs
Kidney
Pancreas
What are some of the visceral systems?
Digestive
Respiratory
Urogenital
Circulatory
What is the structure of a hollow viscus?
Lumen
Mucosa
Muscularis
Serosa
What is the function of the serosa?
Minimise friction of organ against surrounding surfaces
What is the function of the smooth muscle?
1/ Motility: Can contract in waves: peristalsis
2/ Expansion
What is special about the mucosa?
Folded in to increase surface area for absorption
What are constrictions?
This is where the lumen of a hollow organ is narrower
Where are constrictions usually found?
Beginning
End
Other sites along the way
What are dilations?
Give an example
This is a widening in the diameter of the lumen
eg. The bladder
Where are extra constrictions found in the urogenital system?
Where urethra penetrates the pelvic floor
What is an oriface?
Give an example
An opening
Eg. where the ureter goes into the bladder
Where is a calculus likely to be lodged?
At an oriface - ie, where there is a constriction
What can IVP staining tell us?
This makes the urine visible on X Ray
Shows us where urine is not being able to flow
–> shows site of calculus blockage
Describe the structure of the smooth muscle in the muscularis layer of a hollow organ
Two layers:
- inner circular
- outer longitudinal
How can large volumes of liquids be stored in the bladder?
The smooth muscle in the bladder allows expansion of the organs without change in force of contraction
When is micturition brought about?
- Critical stretch of bladder
- Reflex initiated
- Micturition
What reduces friction of solid viscera?
External capsule
What is an exocrine gland?
Cluster of cells that secrete products into a duct
What is an endocrine gland?
Cluster of cells that secrete products into the blood
What are the subdivisions of a solid viscus?
Outer cortex
Inner medulla
How are solid viscera organised?
Lobes
- structural (lungs)
- functional (prostate)
Is medulla outer or inner
Inner
What causes grooves and impressions?
Viscera pressing against solid viscera
Describe an example of grooves and impressions
Aorta: groove on the lung
Heart: impression on the lung
Which type of viscera have sphincters?
Tubular
What are the two different types of sphincters?
What is the difference?
Anatomical:
- surrounded by a thickened ring of muscle
Functional:
- no localised muscle thickening
What is the function of sphincters?
To ensure unidirectional flow of contents of tubular viscus
Where are sphincters commonly found?
Distal ends of ducts
Near external oriface
What controls flow in functional sphincters?
Tube sits obliquely in the muscle
What is the difference between voluntary and involuntary sphincters
Involuntary:
- autonomic innervation
- smooth muscle
Voluntary:
- somatic innervation
- skeletal muscle
Describe the innervation in the anal sphincters
Two lines of defence:
voluntary and involuntary sphincters
Where are serous membranes found?
Covering viscus
Lines body cavity
What are the subdivisions of serous membranes?
- Parietal: lining cavity
- Visceral: covers organ
Compare source of blood supply and innervation of parietal and visceral serous membrane
Visceral:
from the organ
Parietal:
from the muscle of the body wall
What is another name for the parietal serous membrane?
Somatic
What is the name of the serous membrane in the abdomen?
Peritoneum
What is the name of the cavity in the abdomen?
Peritoneal cavity
Describe the arrangement of organs in the abdominal compartment
Suspended by mesentery
What is the role of the mesentery?
1/ Pathway for vessel and nerves
2/ Mobility of the organ
Viscera suspended by mesentery are susceptible to…?
Torsion
- -> cut off blood supply to organ
- -> necrosis of organ
What is referred pain?
This is when pain from an organ is experienced on the skin of the corresponding dermatome
To where is pain usually referred?
The skin
Describe referred pain in the heart
Heart supplied by T1-5
Pain referred to:
Chest: T2-5
Arm: T1
Which organs have a sensory mapping on the brain?
Which don’t?
Mapping:
Somatic innervation
eg. Hands, skin, etc.
No mapping:
viscera, autonomic innervation
Where do paired viscera develop and grow?
What about unpaired viscera?
Paired: On one side of the body
Unpaired: in the midline
Describe referred pain of paired viscera
Since each of the pair has its own innervation and blood supply on each side, only the skin on one side will experience the pain
Describe referred pain of unpaired viscera
Referred pain to local overlying skin of the midline
Which unpaired organs commonly refer pain to the midline?
Viscera of GIT
- appendix
- pancreas
Compare innervation of paired and unpaired organs
Paired:
- each receives innervation from one side of the spinal cord
Unpaired:
- the organs receives innervation from both sides of the spinal cord
