CSMLS Histology Fixation Questions and answers 100% verified.

CSMLS Histology Fixation Questions and answers 100% verified. The primary purpose of fixation is to: a. stop enzymatic action b. remove the water from the tissue c. provide support for the tissue d. autolyze the tissue - correct answers.a. enzymes are proteins and rendered inactive by fixation Which of the following fixatives contains picric acid, formalin and acetic acid a. Zenker b. Helly c. Bouin d. Zamboni - correct answers.c. Bouin The ratio of fixative to tissue should be a. 1:2 b. 5:10 c.15:20 d. 25:50 - correct answers.c. 15 times to 20 times Tissue must be washed in running water after fixation in: a. Zenker solution b. absolute alcohol c. glyoxal d. formalin - correct answers.a. a pigment may be formed when tissue is taken from a chromate-containing solution directly into alcoholic solution Which of the following fixatives contains formalin, potassium dichromate and mercuric chloride a. Zenker b. Helly c. Carnoy d. Orth - correct answers.b. Helly Precipitate left in tissues that have been fixed in solutions containing mercuric chloride may be removed by immersion in: a. running water b. sodium thiosulfate c. weak ammonia water d. iodine - correct answers.d. either Gram or Lugol iodine Commercial stock formaldehyde solutions contain: a. 4% formaldehyde b. 10% formaldehyde c. 37% to 40% formaldehyde d. 98% to 100% formaldehyde - correct answers.c. 37% to 40 % formaldehyde; diluted 1:10 for use Formalin pigment would most certainly be formed when the pH of the formalin is: a. 5.0 b. 6.0 c. 7.0 d. 8.0 - correct answers.a. 5.0. While it is likely to happen with a pH of 6.0 it would most certainly happen with pH of 5.0 Formalin pigment may be removed from tissue by a. running water b. alcoholic iodine c. alcoholic picric acid d. potassium permanganate - correct answers.c. alcoholic picric acid 10% formalin is the same as: a. 3 7% to 40% formaldehyde b. 10% formaldehyde c. 4% formaldehyde d. 1% formaldehyde - correct answers.c. 10% formalin is a 1:10 dilution of 37% to 4% formaldehyde; therefore a 10% solution is the same as 3.7-4 % formaldehyde For best results when using formalin as a routine fixative, it must be made a. acidic b. basic c. neutral d. isoelectric - correct answers.c. The best results are obtained when formalin is neutral as it is as close to physiological pH. This prevents the formation of formalin pigment. Absolute alcohol is indicated as a primary fixative if the tissue is to be processed for the demonstration of: a. fat b. immunofluorescence c. enzymes d. urate crystals - correct answers.d. Urate crystals are soluble in aqueous solution, therefore, absolute alcohol is indicated for fixation Putrefaction of tissue is caused by: a. enzymatic activity b. bacterial action c. aqueous fixatives d. overfixation - correct answers.b. bacterial action To prepare a 10% solution of formalin, which of the following amounts of water should be added to 100 mL of stock formaldehyde? a. 1,000 mL b. 900 mL c. 450 mL d. 10 mL - correct answers.b. 10% formalin is a 1:10 of stock formaldehyde (100% formalin). therefore 100mL of stock + 900mL of water = 1,000mL of a 1:10 dilution The ratio of stock solution to acid in Zenker fixative is: a. 95 parts stock to 5 parts hydrochloric acid b. 95 parts stock to 5 parts acetic acid c. 95 parts stock to 5 parts formaldehyde d. 99 parts stock to 1 part acetic acid - correct answers.b. 5mL acetic aid is added to every 95mL of Zenker/ Helly stock to prepare 100mL of fixative. Formaldehyde is used in Helly solution not Zenker. Which of the following tissue changes will occur if acetic acid is used alone as a fixative? a. swelling b. shrinkage c. over hardening d. poor nucleoprotein preservation - correct answers.a. acetic acid swells tissue and is used in some fixatives to counteract swelling A good fixative for CNS tissue to be stained w/ silver or gold techniques is: a. Zenker solution b. neutral-buffered formalin