Biology 1-2

Respiration The respiratory system handles gas exchange between the body and the environment. Brings in oxygen and removes carbon dioxide. Oxygen is for cellular respiration. Carbon dioxide is made during cellular respiration.

The Respiratory System Oxygen enters the body through the nasal cavity. Incoming air is warmed, filtered and sampled for odors. Molecules land in olfactory organs, stimulating nerve endings and sending signals to the brain. Located at the top of the nasal cavity. Brain interprets the signals as odors.

The Larynx Passes from the nasal cavity to the pharynx and into the larynx. Sits in front of the esophagus and made of cartilage. Cartilage-a tough, flexible connective tissue.

The Larynx cont’d The larynx connects the pharynx to the trachea. Contains the vocal cords. Speech occurs when air leaving the lungs vibrates the vocal cords. The mouth, larynx and tongue shape the air, creating different sounds.

The Trachea and Lungs The trachea carries oxygen to the lungs. Made of rings of cartilage. Lung-internal sac, lined with moist epithelial tissue where gas exchange takes place.

Trachea and Lungs cont’d The trachea splits into two bronchi (left and right bronchus) before entering the lungs. Made of cartilage. Inside of each lung the bronchus splits numerous times into smaller and smaller tubes called bronchioles.

The Alveoli Each bronchiole ends in a cluster of air sacs called alveoli. Each alveolus is made of a thin layer of epithelial tissue.

Alveoli cont’d The alveolus is where oxygen enters the blood and carbon dioxide leaves. Alveoli increase surface area without increasing lung volume.

Alveoli cont’d The passageways and tissues of the respiratory system are coated with mucus and lined with cilia. Mucus traps foreign particles, preventing them from harming the lungs. Cilia-small hair-like fibers. Beat together in a rhythmic fashion to remove particles from the lungs.

Breathing The size of the lungs is controlled by muscles in the chest. The diaphragm is a sheet of muscle directly under the lungs. The intercostals are between the ribs.

Breathing cont’d Inhalation begins at a signal from the brain. Diaphragm and intercostals contract, widening and lengthening the lungs. Air pulled in. Diaphragm and intercostals relax, lungs shrink back to normal size. Air is exhaled.

Breathing cont’d Red blood cells carry oxygen. Red blood cells have a protein, hemoglobin, that is attracted to both oxygen and carbon dioxide. Oxygen in the blood bonds to hemoglobin and is carried from the lungs.

Breathing cont’d Oxygen enters the blood along its concentration gradient. PO 2 lungs > PO 2 blood > PO 2 tissues Carbon dioxide is the reverse. PCO 2 tissues > PCO 2 blood > PCO 2 lungs CO 2 levels are monitored and used to adjust breathing. High CO2 levels increases breathing rate.

Breathing cont’d Two areas in the brain control breathing. Medulla oblongata- creates the signals that make the muscles contract and relax. Pons-smoothes out the basic rhythm set by the medulla oblongata.