The gastrointestinal wall is composed of four layers or tunics:
- Mucosa
- Submucosa
- Muscularis mucosa
- Serosa
The innermost tunic of the wall is known as the mucosa or mucous membrane layer. The digestive tract's lumen is lined with it. The mucosa comprises epithelium, a layer of lamina propria, a loose layer of connective tissue, and the muscularis mucosa, a thin layer of smooth muscle.
The mucosa is surrounded by a substantial layer of loose connective tissue known as the submucosa. Blood arteries, lymphatic vessels, and neurons are also present in this stratum. The adventitia is a connective tissue that makes up the digestive tract's outermost layer above the diaphragm. It is referred to as serosa below the diaphragm.
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Answer:
a. True, b. False, c.True, d. True
Explanation:
a. Base excision repair is started by a DNA glycosylase that recognizes the changes and removes the altered base by cleavage of the glycosidic bond binding the base and the deoxyribose sugar together.
b. Nucleotide excision repair works by a cut-and patch mechanism that removes their heavy lesions, including pyrimidine dimers and nucleotides . Endonucleases are responsible for the lesion of the damaged strand.
c. Nucleotide excision repair is initiated by the proteins namely UvrA, UvrC, and UvrB in Escherichia coli.
-UvrD (helicase II) later removes the damaged strand
-DNA polymerase I (PolI) fills in the resulting gap.
d. DNA glycolases removes the damaged nitrogenous base.
-It leaves the sugar-phosphate backbone intact and thus creating an apurinic/apyrimidinic site, which is commonly referred to as an AP site.
e. Xeroderma pigmentosum complementation group A(XPA)
-This is an essential protein in the nucleotide excision repair pathway.
- It helps to make a pre-incision complex along with other proteins.
There are 4. Adenine, Thymine, Cytosine, and Guanine
Answer:
Blood flows from the right atrium into the right ventricle through the open tricuspid valve, and from the left atrium into the left ventricle through the open mitral valve
