💡 Explanation (Answer: C)

Mitochondria are organelles responsible for generating most of the cell’s supply of adenosine triphosphate (ATP) through cellular respiration. Because they produce the energy currency of the cell, they are famously termed the “powerhouse.”

💡 Explanation (Answer: D)

A tissue is defined as a group of cells that have a similar structure and function together as a unit. Examples include epithelial, connective, muscle, and nervous tissues.

💡 Explanation (Answer: A)

Capsular cells, also known as satellite glial cells, form a thin sheath around the nerve cell bodies within sensory and autonomic ganglia. They provide structural support and regulate the exchange of nutrients and wastes for the neurons they ensheathe.

💡 Explanation (Answer: C)

The human skull consists of 29 bones in total, including the 8 cranial bones, 14 facial bones, 6 auditory ossicles, and the hyoid bone. These bones provide structure to the head and protection for the brain and sensory organs.

💡 Explanation (Answer: D)

The appendicular skeleton comprises the bones of the upper and lower limbs and the girdles (pectoral and pelvic) that attach them to the central axis. The ribs, face, and cranium are components of the axial skeleton.

💡 Explanation (Answer: A)

The temporomandibular joint is classified as a complex joint because it contains an articular disc that divides the joint cavity. Interphalangeal joints are simple hinge joints without such dividing discs.

💡 Explanation (Answer: D)

Striated muscles are characterized by long, cylindrical fibers rather than short ones. Additionally, they possess distinct light and dark bands (striations) caused by the arrangement of sarcomeres, making both statements incorrect.

💡 Explanation (Answer: D)

Actin is a globular protein that forms microfilaments and is a fundamental component of the muscle contraction mechanism. It interacts with myosin to generate the force required for all muscle movements, including voluntary and involuntary actions.

💡 Explanation (Answer: A)

The dorsal body cavity is located along the posterior of the body and protects the central nervous system. It is subdivided into the cranial cavity, housing the brain, and the spinal cavity, housing the spinal cord.

💡 Explanation (Answer: B)

The cerebellum is located at the back of the brain, below the cerebrum and behind the brainstem. It is primarily responsible for motor control, balance, and coordination of voluntary movements.

💡 Explanation (Answer: C)

The hindbrain consists of the medulla oblongata, pons, and cerebellum, which regulate vital functions and coordination. The cerebrum is the largest part of the brain but is located in the forebrain area.

💡 Explanation (Answer: A)

In an average adult human, blood accounts for approximately 7 to 8 percent of total body weight. This volume is critical for transporting oxygen, nutrients, and waste products throughout the body.

💡 Explanation (Answer: d)

Red blood cells (erythrocytes) typically circulate in the bloodstream for about 120 days. After this period, they are removed from circulation by macrophages in the spleen and liver.

💡 Explanation (Answer: c)

Platelets (thrombocytes) have a relatively short lifespan, circulating in the blood for approximately 9 to 12 days. They play a crucial role in hemostasis and blood clotting before being destroyed by the spleen.

💡 Explanation (Answer: d)

Arteries generally lack valves because the high pressure from the heart maintains unidirectional blood flow. They typically appear reddish in color due to the high concentration of oxygenated hemoglobin in the blood they transport.

💡 Explanation (Answer: c)

The liver produces and secretes bile, a fluid essential for the digestion and absorption of fats. This bile is then stored and concentrated in the gallbladder before being released into the small intestine.