Which human excretory organ breaks down red blood cells and synthesizes urea?

A. lung

B. kidney

C. skin

D. liver

Answer Explanation:

D) liver

- Correct: The liver is the human excretory organ that breaks down red blood cells and synthesizes urea. Red blood cells have a finite lifespan and are continually replaced by new cells produced in the bone marrow. When old or damaged red blood cells are removed from circulation, their components are broken down by macrophages, primarily in the spleen and liver. The liver plays a crucial role in this process by breaking down hemoglobin, the oxygen-carrying protein in red blood cells, into heme and globin. Heme is further broken down into bilirubin, which is excreted in bile and eventually eliminated from the body in feces. Additionally, the liver synthesizes urea as a waste product of protein metabolism, which is excreted by the kidneys in urine.

A) lung

- Incorrect: While the lungs play a role in the excretion of carbon dioxide during respiration, they are not involved in breaking down red blood cells or synthesizing urea.

B) kidney

- Incorrect: The kidneys are responsible for filtering blood to remove waste products and excess substances, such as urea, creatinine, and electrolytes, to produce urine. While the kidneys excrete urea synthesized by the liver, they do not break down red blood cells.

C) skin

- Incorrect: The skin is involved in excreting certain waste products, such as sweat (containing water, electrolytes, and small amounts of urea and other metabolic waste), but it does not break down red blood cells or synthesize urea.

Therefore, the Correct Answer is D.

Q #1: Which of these statements about the pharynx is true?

A. It extends from the nasal and oral cavities superiorly to the esophagus anteriorly.

B. The oropharynx is continuous superiorly with the nasopharynx.

C. The nasopharynx is involved in digestion.

D. The laryngopharynx is composed partially of cartilage.

Answer Explanation

d) The laryngopharynx is composed partially of cartilage.

- True: The statement that the laryngopharynx is composed partially of cartilage is true. The pharynx, commonly known as the throat, is a muscular tube that extends from the base of the skull to the level of the sixth cervical vertebra. It serves as a passageway for both air and food. The pharynx is divided into three regions: the nasopharynx, oropharynx, and laryngopharynx.

a) It extends from the nasal and oral cavities superiorly to the esophagus anteriorly.

- False: The pharynx extends from the nasal and oral cavities superiorly to the esophagus and larynx inferiorly, not anteriorly.

b) The oropharynx is continuous superiorly with the nasopharynx.

- False: The oropharynx is continuous inferiorly with the oral cavity, not superiorly with the nasopharynx. The nasopharynx is continuous superiorly with the nasal cavity.

c) The nasopharynx is involved in digestion.

- False: The nasopharynx is primarily involved in respiration and the passage of air. It contains the openings of the auditory tubes and tonsils but is not directly involved in digestion.
Q #2: Which is a function of the liver in human adults?

A. manufacturing red blood cells

B. producing chemical compounds known as auxins

C. storing the carbohydrate reserve glycogen

D. synthesizing the hormone insulin

Answer Explanation

C) storing the carbohydrate reserve glycogen

- Correct: One of the functions of the liver in human adults is storing the carbohydrate reserve glycogen. Glycogen is a polysaccharide that serves as a storage form of glucose in the body. When blood glucose levels are high, such as after a meal, the liver takes up excess glucose and converts it into glycogen for storage. When blood glucose levels drop, such as between meals or during fasting, the liver breaks down glycogen and releases glucose into the bloodstream to maintain blood sugar levels within a normal range.

A) manufacturing red blood cells

- Incorrect: The primary site of red blood cell production (erythropoiesis) in adults is the bone marrow, not the liver. While the liver is involved in the production of blood proteins and components, such as albumin, clotting factors, and plasma proteins, it is not responsible for manufacturing red blood cells.

B) producing chemical compounds known as auxins

- Incorrect: Auxins are a class of plant hormones involved in various physiological processes, such as cell elongation, apical dominance, and root development. They are not produced by the liver in human adults.

D) synthesizing the hormone insulin

- Incorrect: Insulin is a hormone produced by the pancreas, not the liver. Insulin plays a crucial role in regulating blood sugar levels by facilitating the uptake of glucose into cells for energy production or storage. While the liver responds to insulin by regulating glucose metabolism and storage, it does not synthesize insulin itself.
Q #3: Which of these ingredients in saliva is responsible for activating salivary amylase?

A. mucus

B. phosphate ions

C. chloride ions

D. urea

Answer Explanation

b) phosphate ions

- Correct: Phosphate ions are responsible for activating salivary amylase. Saliva contains salivary amylase (also known as alpha-amylase or ptyalin), which is an enzyme that catalyzes the hydrolysis of starch into maltose and other smaller carbohydrates. However, salivary amylase is only activated in the presence of certain ions, particularly phosphate ions. These ions help to stabilize the enzyme's structure and facilitate its enzymatic activity. Therefore, phosphate ions play a crucial role in the function of salivary amylase.

a) Mucus

- Incorrect: Mucus in saliva serves primarily as a lubricant and protective barrier for the oral mucosa and facilitates swallowing. It does not directly activate salivary amylase

c) Chloride ions

- Incorrect: Chloride ions are electrolytes present in saliva, but they do not directly activate salivary amylase. Instead, they help maintain the osmotic balance and pH of saliva.

d) Urea

- Incorrect: Urea is a waste product found in urine and is not directly involved in the activation of salivary amylase.

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Which human excretory organ breaks down red blood cells and synthesizes urea?

More Questions on TEAS 7 Science

Q #1: Which of these statements about the pharynx is true?

Answer Explanation

Q #2: Which is a function of the liver in human adults?

Answer Explanation

Q #3: Which of these ingredients in saliva is responsible for activating salivary amylase?

Answer Explanation

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