Human Body Systems: Digestion, Respiration, Circulation
The Digestive System
The digestive system is responsible for transforming food into simpler substances that can be used by the cells. It is made up of the digestive tract and digestive glands.
Digestive functions:
- Ingestion
- Digestion
- Absorption
- Egestion
Chewing is a mechanical action by which food is shredded. Insalivation is the process of wrapping food in saliva.
The Respiratory System
The respiratory system is responsible for taking oxygen from the air outside, taking it to the blood, and removing carbon
Read MoreCell Nucleus: Structure and Functions
The Cell Nucleus
The cell nucleus is the largest organelle of the eukaryotic cell. It is a small spherical or oval body and is usually placed in the center of the cell but can also be located in the periphery. Prokaryotic cells have no nuclear membrane, unlike eukaryotes, where it exists and also has the structures explained below:
Structure
In its structure, we can appreciate:
- Nuclear envelope
- Chromatin
- Nucleolus
Nuclear Envelope
This can include:
- Outer membrane: It is continuous with the endoplasmic reticulum
Adrenaline, Insulin, Hormones, Tropism, and Reproduction
Hormones: Adrenaline and Insulin
A hormone is a chemical substance secreted by an endocrine gland. It is carried by the blood, which alters the activity of one or more specific target organs and is then destroyed by the liver.
Chemical Control of Metabolic Activity by Adrenaline
Adrenaline is a hormone secreted by the adrenal glands. When you are frightened or excited, your brain sends impulses along a nerve to your adrenal glands. This makes them secrete adrenaline into the blood.
Adrenaline helps
Read MoreNephrons and Urinary Health: Function, Conditions, and Care
Nephrons: The Functional Units of the Kidney
Each kidney contains about one million nephrons. Nephrons are microscopic tubular structures, approximately 2-3 cm in length and about 5 mm in diameter, capable of forming urine. In their initial part, they have a widened capsule called Bowman’s capsule, which surrounds a ball of blood capillaries known as the glomerulus. The Bowman’s capsule is continuous with a long tubule that is responsible for carrying urine. The tubules forming the collecting ducts
Read MoreDigestive System: Food Digestion and Nutrient Absorption
The digestive system performs the processes of food digestion and absorption of nutrients. These processes require two types of actions:
- Mechanical: This involves the fragmentation of food and the movement of the bolus through the digestive tract via muscle contractions called peristaltic contractions.
- Chemical: This involves the hydrolysis of food by enzymes found in digestive juices and bile. These processes break down food into smaller molecules that can cross the gastrointestinal wall and enter
Cellular Respiration: Krebs Cycle and Oxidative Phosphorylation
Krebs Cycle
Adolf Krebs discovered a series of oxidation-reduction reactions known as the Krebs Cycle. The cycle occurs in the mitochondrial matrix in eukaryotic cells, comprising a set of reactions that oxidize acetyl-coenzyme A to CO2. The molecules NAD+ and FAD collect the electrons and are reduced to NADH and FADH2. These electrons will be transferred to an electron transport chain, regenerating NAD+ and FAD to continue the Krebs Cycle.
Stages of the Krebs Cycle
- Acetyl-coenzyme A binds to oxaloacetate