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Course: MCAT > Unit 2

Lesson 3: Foundation 3: Organ Systems

GI system: Lymphatic function during cirrhosis

Problem

Cirrhosis of the liver is a progressive medical condition characterized by the replacement of healthy liver tissue with non-functional tissue, primarily fibrotic tissue. Major contributing factors to this condition are chronic alcoholism and hepatitis infection. One of the prominent manifestations of cirrhosis is ascites, which occurs when excess lymphatic fluid accumulates in the abdominal cavity, outside the organs. Researchers examining lymphatic dysfunction in cirrhosis performed the following studies.
Experiment 1a
Researchers compared the composition and flow rate of lymph between patients with and without cirrhosis. In the first phase of the study, X-ray computed tomography scans were taken of the thoracic duct, the largest lymphatic vessel in the body, responsible for draining lymph fluid from the lower extremities and abdomen into the bloodstream. The study found that among patients without cirrhosis, the thoracic duct had an average diameter of 5 mm. However, among patients with cirrhosis, the thoracic duct had an average diameter of 8 mm.
Experiment 1b
In the second phase of the study, 1 mL of lymphatic fluid was removed from the thoracic duct using a catheter. It was analyzed for protein content and red blood cells. It was found that among patients with cirrhosis, red blood cells made up 4% percent of the lymph, compared with 0% percent for patients without cirrhosis. Protein content among patients with cirrhosis was found to be approximately 6.4 g/dL compared with 6.7 g/dL for patients without cirrhosis.
Experiment 2
Researchers used an immunohistochemical stain for VEGFR3 (the receptor for VEGF-C, a pro-lymphangiogenic factor) to examine lymphatic vessels obtained from patients without cirrhosis, patients with compensated cirrhosis (without ascites), and patients with decompensated cirrhosis (with ascites). The results of their findings are shown in Figure 1.
Figure 1 Results of immunohistochemical stain for VEGFR3 in study groups
Experiment 2 and Figure 1 adapted from: Savneet Kaur et al. Nano-engineered VEGF-C ameliorates gut lymphatic drainage, portal pressure and ascites in experimental portal hypertension. https://www.medrxiv.org/content/10.1101/2020.12.24.20248815v1.full
Which elements normally help to push lymph forward through lymph vessels?
I. Valves
II. Skeletal muscle contraction
III. Pressure from the heart
Choose 1 answer:
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