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

The Small Intestine: Structure and Function

Structure

It is divided into three parts: the Duodenum, Jejunum, and Ileum. The small intestine represents the largest portion of the digestive tube. Its length varies with the type of feed: it is longer in herbivores and shorter in carnivores.

Function

Its primary function is to perform most of the chemical digestion and absorption of nutrients. For this, it requires that the secretions discharged by the pancreas, liver, and intestinal glands are mixed with chyme through sawing motions and peristaltic waves. After this mixture, chyme becomes chyle, consisting of H₂O, mineral salts, monosaccharides, and amino acids, which are absorbed by the intestinal mucosa to be incorporated into the circulatory... Continue reading "Human Digestive System: Stomach and Intestine Functions" »

The Circulatory System: Blood and Its Components

Composition of Blood

Blood is a red liquid that constantly circulates through blood vessels. It transports cells, nutrients, and oxygen, while collecting carbon dioxide and other waste products that must be expelled. Blood is formed by plasma and blood cells.

• Plasma: Transports nutrients and supports the blood cells.
• Blood Cells:
  • Red Blood Cells (Erythrocytes): Responsible for oxygen transport.
  • White Blood Cells (Leukocytes): Including neutrophils, monocytes, and lymphocytes, crucial for the immune system.
  • Platelets (Thrombocytes): Essential for blood clotting.

Blood Vessels

Blood vessels form a network of channels that distributes blood throughout the body, comprising three main types:

• Arteries: Carry

Central Nervous System (CNS) Components and Protection

The Central Nervous System (CNS) is composed of the brain and spinal cord. It is protected by membrane layers, called the meninges, and bone structures: the skull (for the brain) and the vertebrae (for the spinal cord).

Major CNS Structures Housed in the Cranium

The brain structure housed in the cranium includes the Cerebrum, Cerebellum, and Medulla.

The Cerebrum Structure and Function

The Cerebrum is divided into two hemispheres. Its surface features include protrusions called gyri and depressions called sulci or fissures. The cerebral cortex is the outer part, made up of gray matter that receives information from sense organs, produces response orders, and stores and processes information.... Continue reading "Understanding the Central and Peripheral Nervous Systems" »

The Human Circulatory System

The circulatory system is responsible for distributing food and oxygen around the body and collecting waste products from cells. It consists of blood, the heart, and blood vessels (arteries, veins, and capillaries).

Blood Tissue and Its Components

Blood is a tissue formed by a liquid, plasma, and a set of cells: red blood cells, white blood cells, and platelets.

• Plasma: Composed of 90% water and dissolved substances such as nutrients, salts, waste products, hormones, etc.
• Red Blood Cells (RBC): Responsible for transporting oxygen.
• White Blood Cells: Responsible for phagocytizing microbes and producing antibodies.
• Platelets: Essential for blood clotting.

Heart Anatomy and the Cardiac Cycle

The heart muscle contracts to empty... Continue reading "Human Circulatory and Lymphatic System Functions" »

Key Components of the Immune System

Immune Cells

The immune system relies on various specialized cells to identify and eliminate pathogens:

• Neutrophils: These are phagocytic cells (microphages) that can pass through blood vessel walls in a process called diapedesis.
• Monocytes: These cells can collaborate with macrophages and lymphocytes in immune reactions.
• Lymphocytes: A crucial category of white blood cells, central to the specific immune response.
• Basophils: Contain histamine granules, which, when released, dilate blood vessels and increase capillary permeability.
• Eosinophils: Capable of performing both phagocytosis and diapedesis.

Immune Protein Molecules

Immune protein molecules are synthesized by certain immune cells and are essential for defending... Continue reading "The Body's Defense: Immune Cells, Proteins, and Responses" »

Biological Foundations

Photosynthesis: Energy Capture

Photosynthesis is a vital process that enables plants to convert light energy into chemical energy. This fundamental process, crucial for life, relies on the presence of leaves and pigments to capture solar energy.

Cellular Structures & Nutrient Transport

Unicellular vs. Multicellular Organisms

Unicellular organisms are in direct contact with their external environment. In contrast, multicellular organisms do not have all their cells in direct contact with the outside world, facing challenges in spreading nutrients across individual cells.

Therefore, multicellular organisms require internal transport systems (like 'pipes' or circulatory systems) to distribute nutrients to all cells not in... Continue reading "Biological Foundations and Wastewater Treatment Essentials" »

Core Concepts in Ecology

Defining Ecological Units

• Population: A group of organisms of the same species within a defined area that coexist.
• Biotope: The physical environment or place occupied by a community, characterized by environmental conditions such as light or humidity.
• Ecosystem: A community (including different populations) and the biotope in which it is found, where they relate to each other and the physical environment (MDI).
• Environment (MDI): The surroundings of an organism or species, made up of all the factors or conditions that exist in the place where it lives and influence it.

Environmental Factors

Environmental factors include:

• Biotic Factors: Interactions between living organisms, such as the struggle for food or space, or mutual

Core Concepts in Biotechnology and Genetics

Genetic Code

The genetic code is the set of rules by which information encoded in messenger RNA (mRNA) sequences is translated into amino acid sequences during protein synthesis. It dictates which amino acids correspond to each codon, allowing them to join together in the correct position to form a protein.

Biotechnology

Biotechnology involves the use of living organisms, or parts of organisms, or modified products derived from them, to improve plants or animals, or to develop microorganisms for specific objectives.

Plasmids

Plasmids are circular DNA molecules, independent of the chromosomal DNA, that often carry genetic information useful to the host organism, typically found in bacteria and yeasts.

Bacteriophage

The Digestive System: Functions and Anatomy

The digestive system is responsible for several key functions:

• Food intake: Consuming food.
• Nutrient preparation: Breaking down nutrients through mechanical and chemical digestion.
• Absorption: Absorbing nutrients into surrounding tissues.
• Elimination: Eliminating undigested waste.

Components of the Digestive System

The digestive system consists of the following organs:

• Mouth
• Pharynx
• Esophagus
• Stomach
• Intestines:
  • Duodenum
  • Jejunum
  • Ileum
  • Large Intestine (Cecum, Appendix, Ascending Colon, Transverse Colon, Descending Colon, Sigmoid Colon, Rectum, Anal Canal, Anus)

The entire system is lined with the peritoneum, a serous membrane.

Accessory Glands

Several accessory glands aid in digestion:

• Minor and major salivary glands

Endocrine System Fundamentals

What is Endocrinology?

Endocrinology is the science studying the function and pathology of the ductless or endocrine glands, whose secretions are called hormones.

Components of the Endocrine System

The endocrine system is a control system responsible for various bodily functions. It maintains the body's internal environment, participates in growth, sexual differentiation, and reproduction, and intervenes in reactions. Closely related chemically with the nervous system, the endocrine system functions in an integrated way. Endocrine interrelations between glands are most often governed by the hypothalamic-pituitary axis.

The main endocrine glands include the pituitary gland, thyroid gland, endocrine pancreas, parathyroid... Continue reading "Endocrine System and Hormone Function" »