The Digestive and Skeletal Systems: A Comprehensive Overview
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The Digestive System
Functions of the Digestive System
The digestive system performs the following vital functions:
- Breaks down food into molecules the body can use.
- Absorbs molecules into the blood and carries them throughout the body.
- Eliminates wastes from the body.
Types of Digestion
There are two main types of digestion:
- Mechanical Digestion: Foods are physically broken down into smaller pieces.
- Chemical Digestion: Chemicals produced by the body break foods into their smaller chemical building blocks. Most chemical digestion occurs in the stomach.
Key Components and Processes
Saliva
Saliva is the fluid released when your mouth waters. It is produced by salivary glands and plays an important role in chemical digestive processes.
Teeth
- Incisors: Central teeth that cut food into bite-sized pieces.
- Canines: Sharp, pointy teeth that tear and slash food into smaller pieces.
- Premolars and Molars: Crush and grind the food.
Stomach
Most mechanical digestion occurs in the stomach. The stomach contains digestive juice, which includes:
- The enzyme pepsin
- Hydrochloric acid
- Mucus
Large Intestine
The large intestine is the last section of the digestive system. It has two parts: the colon and the rectum. The large intestine contains helpful bacteria, including vitamin K.
Appendix: The appendix is a small, finger-shaped tube that branches off the first part of the large intestine.
Other Important Structures
- Epiglottis: Prevents food from entering the trachea (windpipe).
- Esophagus: A muscular tube that connects the mouth to the stomach.
- Peristaltic Movements: Involuntary waves of muscle contraction that move food through the digestive tract.
- Liver: Located in the upper portion of the abdomen.
- Bile: A substance that breaks up fat particles.
- Gallbladder: The organ that stores bile.
Small Intestine
Absorption of nutrients primarily occurs in the small intestine. The small intestine consists of three parts: the duodenum, jejunum, and the ileum.
Villi: Millions of tiny, finger-shaped structures in the small intestine that increase the surface area for absorption.
The Skeletal System
Functions of the Skeletal System
The skeletal system provides several essential functions:
- Provides shape and support.
- Enables movement.
- Protects internal organs.
- Produces blood cells.
- Stores certain materials until the body needs them.
Components of the Skeletal System
Appendicular Skeleton
- Clavicle: This bone connects the upper arm to the trunk of the body.
- Scapula: Large, triangular flat bone on the back side of the rib cage. It serves as an attachment point for several muscles.
- Pelvic Girdle: It consists of the coxal bones and sacrum.
Cranial Bones
These bones make up the protective frame around the brain.
- Frontal: Forms the forehead, the upper orbit of the eye, and the forward parts of the cranium.
- Parietal: Two parietal bones form the largest portion of the top and sides of the cranium.
- Temporal: Two temporal bones form the lower, central sides of the skull around the external ear.
- Occipital: Forms the back base of the skull. Many neck muscles attach here.
- Sphenoid: Two sphenoid bones sit behind the eyes and run back towards the temporal bones.
- Ethmoid: Forms medial portions of the orbits and the roof of the nasal cavity.
Facial Bones
These bones make up the upper and lower jaw and other facial structures.
- Mandible: The lower jaw. It is the only moveable bone in the skull and articulates with the temporal bone.
- Maxilla: Two maxillae bones form the upper jaw and part of the nose, orbits, and the roof of the mouth.
- Nasal: Two small, slender bones that support the bridge of the nose.
- Lacrimal: Two small lacrimal bones sit at the inside corner of each eye.
- Zygomatic: Two zygomatic bones sit on either side of the skull and comprise the higher area of the cheek.