Respiratory System in Humans (Pulmonary Respiration)

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The Human respiratory system consists of external nares or nostrils, nasal cavity, pharynx, larynx, trachea, bronchi, bronchiole and lungs. Air enters into the nasal cavity through the nostrils. The nasal cavity opens into the posterior part of pharynx. The pharynx leads into trachea or windpipe through a slit called glottis. While swallowing food, glottis gets covered by a small cartilaginous flap of skin called Epiglottis. The lungs lie in the thoracic cavity, which is separated from the abdominal cavity, by a muscular partition called Diaphragm. Within lungs, bronchi branch into many bronchioles. Each bronchiole terminates in a sac called alveolus or alveolar sac, giving the appearance of a bunch of grapes. Walls of alveoli are extremely thin and covered by blood capillaries. The lungs are covered by two thin membranes called Pleura.

Image showing Human Respiratory System.

Image Showing Human Respiratory System.

Image showing Human Respiratory System.

Respiratory Organs of Human Body

Table Showing Respiratory Organs of Human Body.
Table showing respiratory organs of human body.





Opening of Nose

Filtration of unwanted particles

Nasal cavity

Covered with mucous membrane and cilia

Traps dust, bacteria, warms and moistens the air in the pharynx

Pharynx (Throat)

Muscular Tube

The common passage for both respiratory gases and food moving into digestive passage, separated by epiglottis (Epiglottis is a flap like structure that closes the tracheal opening (opening of the wind pipe) called glottis when food is swallowed).

Larynx (Voice Box)

A small cartilaginous organ with vocal cords: lined by ciliated epithelium

Connects pharynx to the trachea; helps in sound production

Trachea (Wind pipe)

Supported by C-shaped cartilaginous rings to prevent it from collapsing. Trachea divides into two bronchi and enters the two lungs

Passages of air upto bronchi

Bronchus (Plural: Bronchi)

Elastic, ciliated and covered with mucous epithelium

Enters the lungs and divides to form secondary bronchi, tertiary bronchioles and ultimately terminal bronchioles. Together they form the bronchial tree


Small terminal branch of bronchus leading to alveoli

Convey air into alveoli

Alveoli (air sacs0

Supplied with blood capillaries, thin moist

Exchange of Gases.

Image showing Human lungs.

Image Showing Human Lungs.

Image showing Human lungs.

mage showing branching of bronchi upto terminal alveoli.

Image Showing Branching of Bronchi Upto Terminal Alveoli.

mage showing branching of bronchi upto terminal alveoli.