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

Reproduction of Human Beings

It is comprised of the following processes:

• The production of gametes: In specialized reproductive organs.
• Fertilization: Is the union of two gametes within the female reproductive system, forming a single cell, the zygote.
• Zygote development: Inside the female reproductive system.
• Birth: A fully formed baby is born.

Development to Sexual Maturity

Changes from infancy to sexual maturity:

• Primary sexual characters: Are present at birth. These are the sexual organs: the penis in boys, and the vulva and excretory system in girls.
• Secondary sexual characters (Puberty):
  • In children: Deep voice, beard, pubic and underarm hair, increased bone and muscle mass.
  • In girls: High voice, growth of breasts and hips, and pubic and underarm

Siphonaptera (Fleas)

Fleas have three pairs of legs, a segmented body, and are 0.5 to 4 mm in size. They can jump 33 times their size. Ctenidia are hairs on their body. The female spermatheca is where the eggs are stored. They have a complete or holometabolous life cycle. The adult lays eggs, and in three weeks, the larvae emerge. In 9-15 days, the pupa stage is reached, and then the adult. Males and females feed on blood. The larvae feed on the feces of the adult fleas. The pupa is covered with earth and is motionless until the temperature changes.

• Pulex irritans (Human flea)
• Ctenocephalides canis (Dog flea)
• Ctenocephalides felis (Cat flea)
• Xenopsylla cheopis (Rat flea)
• Tunga penetrans: The female introduces itself inside the skin, producing a wound

Electron Transport Chain

Cytochrome P-450 - NADH cytochrome reductase: This enzyme facilitates the hydroxylation of many substrates. Therefore, it is important in the synthesis of steroid hormones and detoxification processes. Cytochrome b5 - cytochrome b5 reductase NADF4: These endoplasmic reticulum (ER) membrane proteins exhibit asymmetry, with one face oriented towards the hyaloplasm and the other towards the lumen. Carbohydrates are attached to lipids and proteins facing the luminal side.

Synthesis of Exportable Proteins (Rough Endoplasmic Reticulum)

The cell synthesizes proteins that either remain within the cell or are exported to other locations. These locations can be extracellular, as products of secretion, or intracellular. Protein synthesis... Continue reading "Endoplasmic Reticulum: Protein and Lipid Synthesis" »

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... Continue reading "Respiratory System and Urine Formation: A Comprehensive Look" »

Asexual Reproduction

Asexual reproduction involves a single individual or vegetative parts giving rise to new organisms through mitosis. These offspring are genetically identical and are considered clones. There are several types:

• Bipartition: Organisms divide through a typical mitosis process, resulting in two new individuals of the same size.
• Budding: Daughter cells are formed of different sizes. During mitosis, a bud forms on the parent body, and one of the nuclei migrates to it. When the bud separates, it forms two cells, one larger than the other.
• Multiple Division: Multiple daughter cells are formed. The nucleus of the stem cell divides repeatedly by mitosis, forming a multi-core structure. The cytoplasm is shared, and each core is surrounded

Background

Medical History

• Morbid background
• Chronic respiratory diseases (presence or absence)
• Thoracic surgery history
• Injuries

Reproductive History

• Relevant for therapeutic and diagnostic decisions
• Reproductive age
• Contraceptive methods
• Catamenial regimen

Habits

• Crucial for diagnosis
• Snuff: type, frequency, duration, mode, passive exposure
• Pack-years (e.g., 1 pack/day for 1 year = 1 pack-year)
• Alcohol consumption
• Animal breeding (mammals, birds)
• Biomass fuel use

Drug Use History

• Impact on diagnosis and treatment
• Effects on bronchial kinetics
• Effects on lung morphology
• Influence on respiratory comorbidities

• ACE inhibitors
• Beta-blockers (e.g., propranolol)
• Antineoplastics (e.g., bleomycin, doxorubicin)
• Antiarrhythmics (e.g., amiodarone)
• Nitrofurantoin, methotrexate
• Calcium,

DNA Structure and Function

DNA is a large molecule formed by the union of simpler molecules called nucleotides. The nucleotides correspond to the links of a long chain and consist of:

• A molecule of phosphoric acid
• A carbohydrate called deoxyribose
• A nitrogenous base (adenine (A), guanine (G), cytosine (C), or thymine (T))

The DNA sequence is the order of DNA nucleotides. Each DNA molecule is composed of two long chains of nucleotides coiled up in a double helix. The two strands are chemically complementary. This is because the nitrogenous bases are joined and locked inside the double helix, with specific pairings: (A = T), (T = A), (C = G), and (G = C).

DNA Replication

The DNA molecule is the only molecule in living beings that can make an exact copy... Continue reading "DNA Structure, Replication, and Biotechnology" »

The Human Digestive System

The digestive process begins in the **mouth**. The first processes are chewing, conducted by teeth (*incisors, canines, molars, and premolars*), and salivation, managed by a muscular organ called the tongue. The **tongue** moves food during chewing and contains **taste buds** for sensing flavor. During salivation, food is broken down by teeth and moistened by **saliva**, a watery secretion produced by the **salivary glands**. Saliva production can be triggered by the sight or smell of food. Saliva contains **mucin**, which gives it viscosity, and enzymes such as **salivary amylase** and **lingual lipase** (which hydrolyzes milk fat).

The ground food and saliva form the **bolus**, which is pushed into the **esophagus*... Continue reading "Human Digestive and Respiratory Systems: A Detailed Look" »

The Male Reproductive System and Gametes

• Testicles: Glands in the scrotum that produce sperm.
• Prostate Gland: A walnut-sized gland surrounding the urethra. It produces a prostatic fluid that protects the sperm against the acidity of the urethra and vagina.
• Ductus Deferens (Vas Deferens): Tubes that are a continuation of the epididymis and converge in the urethra.
• Seminal Vesicles: Glands that produce seminal fluid, in which sperm swim. This fluid empties into the ductus deferens.
• Urethra: Duct that communicates with the outside. Its muscular walls contract rhythmically during ejaculation, propelling the sperm.
• Epididymis: A long, very thin, coiled tube located on each testicle. Sperm mature inside it.
• Penis: A cylindrical organ, whose widened end,

Phases of Infectious Diseases

All infectious illnesses typically follow three phases:

• Incubation: The time that elapses between infection and the appearance of disease symptoms.
• Overt Disease: Symptoms and signs of the disease are clear.
• Convalescence: The phase when the pathogens are completely eliminated. The body recovers lost health and repairs damage.

Prevention of Infectious Diseases

Prevention involves two main approaches:

• Following healthy lifestyle habits.
• Vaccination: The introduction of killed or weakened microorganisms into a healthy person's body, prompting the immune system to produce antibodies against the specific disease.

Treating Infectious Diseases

Treatment often involves chemotherapy, which is the use of chemical substances. There... Continue reading "Infectious & Non-Infectious Diseases: Phases & Treatments" »