Human Body: Nutrient Absorption and Respiratory System
Nutrient Absorption
Absorption is the process by which nutrients, obtained through digestion, cross the intestinal wall into the circulatory system. From there, they are distributed to all of the body’s cells.
How Absorption is Carried Out
- Most organic nutrients are absorbed in the small intestine. They cross the plasma membrane of the cells in the intestinal mucosa and travel towards the intestinal villi, which are made up of a network of capillaries. Nutrients then pass through these capillaries
Human Sensory and Coordination Systems: A Deep Dive
Sensory Receptors in Humans
Receptors are the structures human beings use to detect stimuli.
- Interoceptors: Also known as internal receptors, collect information about the human body’s internal conditions. These receptors, located in the internal environment, mostly respond to chemical stimuli (e.g., oxygen in blood).
- Exteroceptors: Also known as external receptors, provide information from the body’s outside environment and are therefore located on the surface of the body. Sense organs are exteroceptors.
Understanding Fertilization and Embryonic Development
Fertilization and Embryonic Development
Fertilization is a chemical process by which the sperm penetrates the egg. There are two types of fertilization: internal and external.
- Internal fertilization occurs when sexual intercourse takes place. In this case, millions of sperm are expelled and enter the vagina.
- External fertilization occurs when sperm swim in the water to fertilize the eggs released by the female.
Segmentation
During this stage, the zygote undergoes a number of divisions that produce large
Read MoreNervous System and Sensory Organs: Structure, Function, and Disorders
Cells of the Nervous System
The nervous system is formed by very distinct cells. Neurons are the cells responsible for conducting nerve impulses. Neurons communicate by connecting the axon with the dendrites.
Types of Neurons
- Sensory or afferent neurons
- Interneurons or association neurons
- Motor neurons
Sensory Receptors
Receptors are a set of specialized cells that perceive stimuli. According to the stimulus, they are classified as:
- Thermoreceptors
- Chemoreceptors
- Mechanoreceptors
- Photoreceptors
Internal receptors
Read MoreAnimal Kingdom: Characteristics of Major Phyla
Phylum Porifera
Phylum Porifera, consisting of 5,500 species, are the simplest animals that exist and are sessile. Their bodies are pierced by pores that communicate with the gastrocele, covered by choanocytes. They have radial symmetry and their skeletons consist of spicules. Examples: Sponges.
Phylum Cnidaria
Phylum Cnidaria, with 10,000 species, are lower animals with more differentiated tissues. They are shaped like a polyp (sessile sack) or jellyfish (free-floating). The surface of their bodies
Read MoreCell Components and Their Functions
Cell Organelles: Structure and Function
1. Plasma Membrane (Cell Membrane)
Structure: A bilipid membranous layer composed of proteins and carbohydrates. It is fluid-like.
Function: The cell membrane separates the cell from its external environment and is selectively permeable, controlling what gets in and out. It protects the cell and provides stability. Proteins are found embedded within the plasma membrane, with some extending all the way through in order to transport materials. Carbohydrates are
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