Biology Test 352

Androgens regulate the development, maturation, and function of male accessory sex organs (epididymis, vas deferens, seminal vesicles, prostate gland, urethra). They stimulate muscular growth, facial and axillary hair growth, aggressiveness, and a low-pitched voice. Androgens play a key role in spermatogenesis and influence male sexual behavior (libido). They also have anabolic effects on protein and carbohydrate metabolism

Intercostal muscles (external intercostal & internal intercostal) are attached to the ribs which help in the movement of the rib cage during breathing.

The diaphragm plays an important role in inspiration and expiration. It consists of internal and external intercostal muscles. The contraction of the diaphragm and the internal intercostal muscles causes an increase in the volume of the thoracic chamber resulting in inspiration. The relaxation of diaphragm and intercostal muscles results in expiration. A hiccup is caused due to the muscular spasm of the diaphragm.

Expiratory reserve volume is the extra amount of air that can be expired forcibly after a normal expiration. It is about 1000-1500 mL. Inspiratory Reserve Volume = 2000 mL.

Vital capacity = 4000mL

Total lung capacity = 5000mL

The diaphragm is the primary muscle used in the process of respiration. The dome-shaped muscle is located just below the lungs and heart. Expiration is a process by which CO₂ expells out from the lungs. Muscle fibres of the diaphragm relax to make it convex and decreasing the volume of the thoracic cavity.

Vital capacity of lungs is the maximum volume of air a person can breathe in after forced expiration. This includes ERV, TV, and IRV or the maximum volume of air a person can breathe out after a forced inspiration.

VC = TV + ERV + RV

Total lung capacity is the sum of the vital capacity and residual volume i.e.,

TLC = VC + RV

Hence, VC = TV - RV

The trachea is a straight tube extending up to the mid-thoracic cavity, which divides at the level of the 5^th thoracic vertebra into a right and left primary bronchi. Each of the bronchi undergoes repeated divisions to form the secondary and tertiary bronchi and bronchioles ending up in very thin terminal bronchioles. The tracheae, primary, secondary and tertiary bronchi, and initial bronchioles are supported by incomplete cartilaginous rings. Each terminal bronchiole gives rise to a number of very thin, irregular walled and vascularised bag-like structures called alveoli. The branching network of bronchi, bronchioles and alveoli comprises the lungs.

Dust is a type of particulate matter. If in an environment the particulate matter is present whose size is 100 mm, then it is known as dust. Mineral dust is produced from the breakdown of parents rock into mineral. These minerals get mixed with air, and their quantity into it will increase if we put more energy into the work. The dust contains silica, asbestos, etc.

The inhalation of silica dust causes silicosis. When silica directly enters into the blood of the human, they affect lungs over there. It reduces the ability of lungs in taking oxygen. As a result, lungs become more susceptible to one more disease, i.e., tuberculosis. This is known as pneumoconiosis. Similarly, when a person inhales asbestos, it causes asbestosis. It also shows effects on the lungs. There is no cure present for this. To control dust exposure generally, the water spray is done. This mineral dust causes inflammation. If it persists for a long time in the lungs, then it causes cancer. Scarring in the lung tissue is apparent when it is diagnosed with a CT scan.

Damage to alveolar walls causes loss in surface area for exchange of gases. Especially seen in emphysema. Spasm of bronchial wall occurs by hypersensitivity reaction where substances are released from mast cells or basophils.

Accumulation of fluid in the pleural cavity is known as pleural effusion. The most common cause is trauma or infection.

Statement B and C are wrong, because inspiration occurs if the pressure within the lungs (intra-pulmonary pressure) is less than the atmospheric pressure, i.e., there is a negative pressure in the lungs with respect to atmospheric pressure. Expiration takes place when the intra-pulmonary pressure is higher than the atmospheric pressure, i.e., there is positive pressure in the lungs with respect to atmospheric pressure.

i. Reptiles, birds and mammals possess negative pressure breathing.

ii. The impulses for voluntary breathing are sent by the medulla oblongata.

iii. The primary, secondary and tertiary bronchi are supported by incomplete cartilaginous rings.

iv. The volume of air remaining in the lungs after a normal expiration is known as functional residual capacity (FRC). It includes expiratory reserve volume (ERV) and residual volume (RV). ERV is the maximum volume of air that can be exhaled after a normal expiration. It is approximately 1000–1500 mL.