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

Achalasia: Esophageal Motility Disorder

Achalasia is a disorder of esophageal motility characterized by decreased peristalsis and a failure of the lower esophageal sphincter (LES) to relax. The etiology is unknown. As the sphincter fails to relax, food accumulates in the lower esophagus within the thoracic cavity. The esophagus becomes dilated, its walls hypertrophied, and food does not pass until it accumulates enough to force its way through.

Clinical Manifestations of Achalasia

Symptoms result from the difficulty of food passing through the esophagus into the stomach. These may include:

• Food regurgitation
• Burning and retrosternal pain after meals, which may increase or decrease with movement

Diagnostic Procedures for Achalasia

Diagnosis is typically... Continue reading "Achalasia, Esophageal Diverticula, and Gastritis: Symptoms and Treatments" »

The Human Ear and Hearing Process

The ear consists of three main parts:

• Outer Ear: Formed by the auricle (pinna) and the ear canal. The canal is protected by auditory wax and ends at the eardrum (tympanic membrane).
• Middle Ear: Contains three tiny bones called ossicles: the malleus (hammer), incus (anvil), and stapes (stirrup).
• Inner Ear: The deepest part, formed by the membranous labyrinth, which is contained within the bony labyrinth. Between these two labyrinths is perilymph, and within the membranous labyrinth is endolymph. The membranous labyrinth includes the cochlea (a snail-shaped structure responsible for detecting sounds) and the vestibular apparatus (involved in balance).

How Sound Perception Occurs

When sound waves reach the eardrum,... Continue reading "Human Body Systems: Hearing, Touch, Bones, and Joints Explained" »

The menstrual cycle is the process by which people develop female gametes (oocytes, ova) and produce a series of changes designed to establish a possible pregnancy. The beginning of the cycle is defined as the first day of menstruation, and the end of the cycle is the day before the start of the next menstruation. The mean cycle length is 28 days, although this may be longer or shorter.

The first menstruation is termed menarche, and the last is known as menopause. Depending on the changes in the ovary and uterus, the menstrual cycle is divided into two phases:

• Follicular phase: From the first day of menstruation until ovulation, which consists of menstruation and the proliferative phase.
• Luteal phase: From ovulation until the first day of menstruation,

The Respiratory System

The respiratory system is responsible for ensuring the supply of oxygen to body cells and removing carbon dioxide. Blood oxygenation is a process that occurs through gas exchange between the blood vessels and the pulmonary alveoli. The respiratory system also prevents the entry of unwanted elements and the development of infections.

Anatomy of the Respiratory System

The respiratory system consists of various organs, which are divided into:

Upper Airways

Located outside the thoracic cavity, including the nose, nares, pharynx, and larynx.

Lower Airways

Located inside the chest cavity, including the trachea, bronchi, bronchioles, alveoli, lungs, and pleura.

Upper Respiratory Tract

1. Nose

   The air enters through the nostrils, right and

Operation of the Nephron

Filtration of blood occurs as it passes through the glomerulus. Substances pass into the renal tubule, small molecules but not large molecules or cells. This process forms the primary urine.

Reabsorption of useful substances, such as glucose, amino acids, and over 90% of the water, takes place along the renal tubule.

Secretion of noxious substances, such as urea or some mineral salts, from the capillaries into the renal tubule, continues along the entire duct, so that inside it, concentrated urine is formed. This is drained into a collecting duct, common to many nephrons, which flows into the renal pelvis. As a result of the process, blood from the kidneys, via the renal veins, is cleansed of waste products.

Average Domestic

Interstitial

Chemistry of Life

The universe is mainly composed of Hydrogen (H) and Helium (He). The Earth's crust is composed of Silicon (Si), Iron (Fe), Magnesium (Mg), and carbon (C). Living organisms form organic macromolecules. Oxygen and Hydrogen constitute 68-70% of living matter (Water = H₂O). Nitrogen (N) is part of proteins.

Properties of Living Beings

Living beings are complex materials that can interact with the world around them and reproduce.

Features

• Made mostly of Carbon and H₂O
• Their reactions inside cells are governed by the laws of physics and chemistry.
• They reproduce

Interaction with the Environment

Living beings evolve and react to external or internal stimuli, creating responses through the nervous and endocrine systems (hormones).

Nutrition

Living... Continue reading "Chemical Composition and Functions of Living Beings" »

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... Continue reading "Bacterial Basics: Gram Staining, Morphology, and Reproduction" »

Understanding Diet and Nutrition

What is Diet?

Diet: The amount and type of food we consume.

Types of Diets

Balanced Diet: A healthy diet provides the body with the right amount of energy and different types of nutrients.

Mediterranean Diet: This is a balanced diet that combines all foods properly.

Genetically Modified Organisms

GMO Foods: These are produced from organisms that have had genetic material from another living being introduced.

Food Preservation and Additives

Food Preservation Methods

Food can be preserved using chemical and physical methods:

• Heating foods to high temperatures for a few seconds can eliminate a number of bacteria.
• Preservation by cold (refrigeration/freezing).
• Freeze-drying eliminates water from food.
• Chemical preservation uses

Sun Energy and Life

The ecosphere is a hypothetical spherical zone located around any star, such as the Sun, where temperatures and appropriate conditions exist to allow living things to originate and evolve.

What is an Ecosystem?

An ecosystem is a particular area where environmental conditions allow some organisms to develop concretely.

• Biotope: The physical environment in which an ecosystem is stable.
• Biocenosis: All living beings inhabiting a biotope.

Factors of an Ecosystem

They fall into two types:

• Abiotic factors: All environmental factors in an ecosystem.
• Biotic factors: Establishing relationships between living things in an ecosystem.

What Effect do Abiotic Factors Have on Living Beings?

They can be:

• Climatic factors (temperature, rainfall, and

Asexual Reproduction in Animals

This is a reproductive process in which new individuals arise from the somatic cells of a single parent. It is common in less evolved animals.

Budding

This consists of the formation of a multicellular outgrowth (bud) on the parent animal's body. Later, these buds may separate to form an independent adult, or they may remain attached, giving rise to colonies, as seen in corals.

Fragmentation (Excision)

The parent body divides into two or more parts, each capable of regenerating into a new animal. Fragmentation can be:

• Longitudinal: Division occurs parallel to the main body axis.
• Transverse: Division occurs perpendicular to the main body axis.

Strobilation

This is a form of multiple transverse fragmentation found in some... Continue reading "Animal Reproduction: Asexual and Sexual Methods" »