Notes, summaries, assignments, exams, and exercises for Biology for Secondary education

Respiratory System Anatomy and Function

The respiratory system is composed of the following key components:

• Nostrils
• Pharynx
• Larynx
• Trachea
• Bronchi and Bronchioles
• Lungs
• Pulmonary Alveoli
• Diaphragm

Nostrils: Air Filtration and Warming

The nostrils are two channels located at the base of the nose, leading to the nasal cavity. The nasal cavity is separated by the septum. Nasal hairs filter the air, trapping dust and particles. The interior is lined by the nasal mucosa, which warms and humidifies the inhaled air. Their primary function is to allow air entry into the body.

Pharynx: The Throat's Passageway

The pharynx, a tube approximately 14 cm long, connects the nasal passages, oral cavity, larynx, esophagus, and middle ear. From the pharynx, air is directed...

Part II: The Endocrine System

Endocrine System Function

The endocrine, or hormonal, system is another system of coordination within the body. This system is closely related to the nervous system, and they are dependent on each other. In some cases, the nervous system stimulates or inhibits the secretion of hormones, and in others, the hormones stimulate or inhibit the action of the nervous system.

The endocrine system consists of a series of glands located throughout the body. These glands, called endocrine glands, are not anatomically connected to each other. They pour their secretions directly into the bloodstream.

Endocrine glands are formed by specialized secretory cells that synthesize chemicals called hormones. Once produced, hormones are...

Cellular Components and Their Functions

Lysosome

Features: Lysosomes are vesicles containing substances that digest nutrients.

Function: They break down more complex substances into simpler ones.

Centrosomes

Features: Centrosomes are located near the nucleus and consist of two perpendicular cylinders formed by proteins.

Function: They are involved in cell division and the formation of cilia and flagella.

Understanding Health and Disease

Disease

Definition: A disease occurs when a part of the body is altered and can no longer perform its function properly, leading to dysfunction.

Health

Definition: The World Health Organization (WHO) defines health as a state of complete physical, mental, and social well-being, not merely the absence of disease.

Symptoms

When...

The Cerebral Cortex and Synaptic Transmission

The cerebral cortex is the highest level of the brain, responsible for controlling the activities of other neurons at lower levels. This demonstrates the hierarchical nature of our nervous system. For instance, while the medulla oblongata (often referred to as 'the bulb' in older texts) controls automatic breathing movements, it also sends signals to the cerebral cortex. This explains why, when we enter water, we can consciously hold our breath, as the cerebral cortex can override the medulla's automatic control.

Understanding the Synapse

A synapse is the specialized space between two neurons that a nerve impulse must traverse to pass from one to another. This crucial process is known as synaptic transmission....

The Respiratory System: How Air Enters Your Body

Air entry is performed through the nostrils and reaches the nasal cavity, where it is warmed. The nasal wall is full of blood vessels. The nostrils open into the pharynx, an organ common to the respiratory and digestive tracts. The inferior pharynx communicates with the larynx, allowing air to enter the trachea.

In the larynx, a cartilaginous lamina, the epiglottis, closes to prevent food from entering the respiratory tract. The larynx, in addition to serving as an air passage, is also a vocal apparatus. Inside the larynx, the vocal cords vibrate as air passes over them, allowing us to produce sounds.

The trachea is lined with a mucous membrane rich in glands that trap dust particles. The walls...

Chemical Language and Genetic Instruction

Genes are DNA molecules; these are carriers of information necessary for the development of a cell or an individual. They are the only molecules capable of self-replicating (making copies of themselves). They perform their function due to the existence of the genetic code. Reading this code, or its expression, results in the synthesis of specific proteins. Genes can be deliberately manipulated by genetic engineering techniques. Genetic manipulation has a wide range of applications, including obtaining drugs, vaccines, disease diagnosis, and gene therapy.

DNA: The Molecule of Heredity

Genes are the carriers of biological information and, therefore, are located within all cells. However, their location was...

The Digestive System

Role of Digestion

During the process of digestion, food is broken down. The broken molecules can then be used by cells.

Digestive Tract Structure

The digestive tract is a duct, a 9-meter long pipe through which food passes, extending from the mouth to the anus.

Glands: Glands pour their juices into the tube. The main glands are the salivary glands, liver, and pancreas.

Food is transported by a wave of contraction and relaxation called peristaltic movements.

Layers of the Digestive System

Internal or Mucosal Layer: This layer secretes digestive juices and mucus, protecting the surface. Nutrients are absorbed through this layer.

Muscularis: This layer consists of involuntary muscle fibers that contract. The anal sphincter muscles...

The Digestive System

Humans need to consume a range of foods from which they obtain the necessary materials and energy for their bodily functions. The body requires proteins, lipids, carbohydrates, vitamins, and minerals.

Understanding Nutrition

Nutrition is the biological function through which living organisms acquire and transform matter and energy from their environment. We can distinguish three main phases in nutrition:

• Ingestion
• Digestion
• Absorption

The digestive system is responsible for transforming food. This process occurs through various parts of the body:

• Mouth
• Pharynx
• Esophagus
• Stomach
• Small Intestine
• Large Intestine
• Anus

Common Dental Diseases

• Gingivitis
• Periodontitis (Pyorrhea)
• Plaque
• Cavities

Diseases of the Digestive System

• Constipation and Diarrhea
• Peptic

Gram Staining: Positive and Negative Bacteria

In bacteria, the cell wall is a determinant of cell shape and has also served as a classification criterion. In 1884, French bacteriologist Christian Gram developed a method to observe bacteria under light microscopy using specific staining. However, not all bacteria are stained with this method, which led to their classification into two groups: Gram-positive bacteria, which retain the stain, and Gram-negative bacteria, which do not retain the stain.

This distinction reflects structural differences in the bacterial cell wall. In Gram-positive bacteria, the wall is mainly composed of peptidoglycan and teichoic acid. In contrast, Gram-negative bacteria have, in addition to peptidoglycan, an outer membrane...