Human Respiratory and Digestive Systems: Key Functions

Respiratory System Components

• 1 Nose
• 2 Mouth
• 3 Larynx
• 4 Right lung
• 5 Right bronchus
• 6 Diaphragm
• 7 Pharynx
• 8 Trachea
• 9 Left bronchus
• 10 Bronchiole
• 11 Alveoli

Characteristics of Alveoli for Gas Exchange

The epithelium of the alveoli is monostratified, consisting of a single layer of extremely flattened epithelial cells. Similarly, the capillary epithelium consists of a single layer of flat cells, known as the endothelium. The alveoli are covered by a vast network of capillaries to facilitate efficient gas exchange.

How Air Is Cleaned, Moistened, and Warmed

The nose filters inhaled air using hairs that trap particles. Additionally, as air passes through the nasal cavity, it is warmed and moistened.

Understanding the Endothelium

The endothelium forms the thin walls of the capillaries. It is composed of a single layer of flat cells designed to ensure the efficient exchange of substances, such as gases and nutrients.

Digestive System Components

• 1 Mouth (tongue)
• 2 Liver
• 3 Ascending colon (large intestine)
• 4 Cecum
• 5 Appendix
• 6 Rectum
• 7 Oesophagus
• 8 Stomach
• 9 Pyloric valve
• 10 Transverse colon
• 11 Small intestine
• 12 Descending colon
• 13 Sigmoid colon

Functions of the Large Intestine

In the large intestine, water is absorbed, and chyle is compacted to form faeces, which are subsequently expelled via the anus.

The Process of Digestion

To digest means to break down food so the body can absorb its nutrients. This occurs in two ways:

• Mechanical digestion: Performed by the teeth and peristaltic movements, breaking large food chunks into smaller pieces.
• Chemical digestion: Performed by digestive enzymes. These proteins break down large molecules like fats, proteins, and carbohydrates into smaller, absorbable molecules. For example, proteases break down proteins, and amylase breaks down starch.

What Are Microvilli?

Microvilli are found on the surface of epithelial cells, such as those lining the intestine. They increase the cell's surface area, thereby facilitating the absorption of nutrients and water molecules.