Notes, summaries, assignments, exams, and problems for Biology

Digestive Systems in Animals

Models of the Digestive Apparatus

• A stomach cavity with one opening, e.g., Porifera.
• A digestive tract with two openings (mouth and anus), i.e., vertebrates.

Digestive Systems in Invertebrates

• Platyhelminthes: Flatworms have a blind tube with a single hole.
• Nematodes: A mouth and an anus appear.
• Annelids: In the digestive tract with a mouth and an anus, specialized structures like the esophagus, crop, and gizzard appear.
• Molluscs: The digestive tract has specialized regions and displays a body attached to the hepatopancreas.
• Echinoderms: The digestive tract has specialized regions in which Aristotle's lantern stands out among the sea urchins.
• Arthropods: They all possess a digestive tract with specialized regions and also

Understanding Autoimmunity

An animal's immunological system can typically recognize its own body's molecules and distinguish them from foreign ones, producing antibodies against foreign substances. However, in rare cases, it produces antibodies against the body's own components. This phenomenon is called autoimmunity.

The consequence of this error is the development of serious diseases. Autoimmunity can be caused by genetic factors and may be inherited.

The body's own molecules that trigger autoimmunity are called autoantigens. Certain proteins can act as autoantigens. An autoimmune response occurs when these proteins are released into the bloodstream due to tissue injury.

Biochemical analysis has revealed that many microbes have evolved a strategy... Continue reading "Immune System Disorders: Autoimmunity & Allergies" »

Postovulatory Phase and Fertilization

The postovulatory phase comprises days 15 to 28 of the menstrual cycle. After the expulsion of the ovum, the follicle degenerates, fat accumulates, and it becomes the corpus luteum. The innermost layer of the uterus gradually thickens and acquires a spongy appearance with numerous glands and blood vessels to nourish a future embryo. If fertilization does not occur, around the 28th day, the thickened layer of the uterus, the endometrium, is destroyed and expelled, along with the remains of the unfertilized egg. This process produces a hemorrhage known as menstruation or a period.

If fertilization occurs, the innermost layer of the uterus remains swollen during pregnancy. The corpus luteum in the ovary continues... Continue reading "Understanding Postovulatory Phase, Fertilization, and Childbirth" »

Heart: Function

The heart is responsible for carrying oxygen in the blood and nutrients to all body cells for proper functioning. It is also in charge of collecting and transporting waste material for disposal.

Heart: Structure

The heart is a hollow organ the size of a fist, located in the center of the left chest between the lungs. It consists of a heart wall and four cavities.

Heart Wall

The heart wall has three parts:

• The endocardium is the innermost layer and is in contact with blood.
• The myocardium is the middle layer, composed of cardiac muscle tissue, and it is thick.
• The pericardium is the outer layer containing liquid, and it also absorbs the friction of the heart.

Cardiac Cavities

The heart is divided into two halves, which in turn are divided... Continue reading "Heart Anatomy and Physiology: Structure and Function" »

Tendon Structure

Tendon: A structure composed of collagen fibers arranged parallel to the tendon's axis. These fibers are designed for low flexibility and resistance to extension. Within the tendon, we find loose connective tissue and cells called tenocytes.

The entire structure is termed the endotendon, enclosed within a sheath called the peritenon. The peritenon's extension is continuous with the periosteum at one end and the perimysium at the other.

Some tendinous fibers, known as Sharpey's fibers, penetrate the bone and calcify, forming a strong union between tendon and bone.

The tendon is protected by an outer sleeve consisting of a parietal layer and an inner visceral synovial layer. A space filled with synovial fluid separates these layers.... Continue reading "Tendon, Fascia, and Cranial Bones: Structure and Function" »

Nervous vs. Endocrine System Coordination

Living organisms utilize different systems for coordination. These include:

• Nervous System: Receives information and processes it for a fast response. It utilizes nerve impulses, and its effects are generally short-lasting.
• Endocrine System: Elaborates hormones for communication. Its response is typically very slow but durable.

Nervous System Response Pathway

The nervous system's response to stimuli involves several key components:

Receptor, Center, and Effector

• Receptor: The organ or structure responsible for perceiving stimuli from the internal or external environment.
• Nervous Center: Receives information from receptors and transmits processed information, producing a series of organized responses.
• Effector:

The Interaction in Living Things

The interaction functions are those enabling a living being to receive information from the outside to the inside, and respond to it. A stimulus is a change in the environment surrounding a body or inside it.

There are two types of responses:

• Static: There is no movement.
• Dynamic or taxis: Movement occurs in response to a stimulus.

The Interaction in Plants

• Tropism: Movements related to plant growth or its parts. They are slow and irreversible responses.
• Nasties: Rapid and temporary changes in certain parts of the plant.
• Photoperiodism: Responses due to changes in illumination that occur throughout the seasons.

The Relationship in Animals (1)

Many animals have developed sophisticated sensory organs that detect specific... Continue reading "Interaction: Stimulus and Response in Living Things" »

Ecosystems: An Overview

Ecology is the science that studies the characteristics of living beings, their environment, and the relationships they build with each other and their surroundings.

What is an Ecosystem?

An ecosystem consists of a fragment of the biosphere where living organisms interact and form relationships.

Biotope

The biotope is the physical environment or place where living things develop, including the environmental conditions that characterize it.

Biocenosis

Biocenosis refers to the set of living organisms within a given ecosystem.

The Biotope: Terrestrial and Aquatic Environments

The terrestrial environment is located on the surface of the continents, while the aquatic environment is made up of water.

Abiotic Factors

Abiotic factors are... Continue reading "Understanding Ecosystems: Biotope, Biocenosis, and Dynamics" »

Human Tissue Types: Location and Function

Epithelial Tissue: This tissue is found on the body's exterior surfaces, lining internal cavities (such as blood vessels), and in glands. Its cells are directly linked, without any intermolecular substance between them. The primary function is to coat and protect the body's exterior and internal cavities.

Connective Tissue: Located around organs, tendons, ligaments, in the dermis of the skin, and bone marrow. It consists of several cell types and connects other organs, muscles, and bones. It also fuels the dermal tissue and generates red blood cells.

Adipose Tissue: Found under the skin and around certain organs (like the kidney or heart). It is composed of round cells that store fat. Its functions include... Continue reading "Human Tissue Types and Cellular Components: Functions" »