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

Human Body and Homeostasis

Cells and Their Functions

Cytoplasm: The material between the plasma membrane and the nucleus, composed of cytosol (largely water with dissolved proteins) and cytoplasmic organelles.

• Mitochondria: Provide ATP (energy).
• Ribosomes: Sites of protein synthesis.
• Endoplasmic Reticulum: Manufactures proteins and catalyzes reactions.
• Golgi Body: Concentrates and packages proteins.
• Lysosomes: Contain digestive enzymes; degrade unwanted substances.
• Cytoskeleton: Provides structural support.
• Nucleus: Control center of the cell; contains genes.
• Centriole: Plays an active role in cell division.
• Microvilli: Increase surface area for absorption.
• Vacuole: Membrane-bound organelle that stores and excretes substances.

Plasma Membrane: Separates... Continue reading "Human Body Systems: A Comprehensive Overview" »

Benign Epithelial Lesions

Squamous Cell Papilloma

Age: Mid-age
Site: Palate, uvula, cheek, lip, tongue, gingiva
Characteristics:

• Color: White to pinkish (depending on keratinization)
• Shape: Cauliflower-like
• Surface: Rough, irregular (finger-like projections)
• Texture: Firm or soft (depending on keratinization)
• Sessile or pedunculated

Histological Features:

1. Hyperplastic stratified squamous epithelium
2. Acanthosis and hyperkeratosis
3. Intact basal layer
4. Thin central branching core of connective tissue carrying nutrition

Verruca Vulgaris (Wart)

Reactive lesion, autoinoculation
Etiology: HPV 2, 4, 6
Histological Features:

1. Intranuclear inclusion bodies
2. Koilocytes
3. Cupping effect of rete ridges
4. Granular cell layer

Keratoacanthoma

True, self-limiting lesion
Age: Older males
... Continue reading "Benign Epithelial and Mesodermal Lesions of the Oral Cavity" »

Circulatory System

Deoxygenated blood from the body returns to the right atrium of the heart through the superior and inferior vena cavae. The right atrium contracts, pushing the blood through the tricuspid valve into the right ventricle. The right ventricle contracts, pumping the deoxygenated blood through the pulmonary valve into the pulmonary artery. The pulmonary artery carries the deoxygenated blood to the lungs, where it picks up oxygen and releases carbon dioxide through the process of gas exchange. Oxygenated blood returns from the lungs to the left atrium of the heart via the pulmonary veins. The left atrium contracts, pushing the oxygenated blood through the mitral valve into the left ventricle. The left ventricle contracts, pumping... Continue reading "Understanding the Circulatory and Reproductive Systems" »

Chromosomes and DNA

Genes are contained within chromosomes, which are made of DNA and located in the cell nucleus. A chromosome contains thousands of genes. Every normal human contains 23 pairs of chromosomes, a total of 46 chromosomes.

Traits and Alleles

A trait is any gene-determined characteristic, often determined by more than one gene. Gene: A segment of DNA that controls a hereditary trait. Alleles are different versions of a gene that produce distinguishable traits in offspring. Two alleles must be present in order for a trait to appear in the offspring. One allele is provided by each parent to the offspring. When fertilization of sperm and eggs occurs, the new offspring will have 2 alleles for each gene.

Gregor Mendel's Contributions

Gregor... Continue reading "Genetics: The Basics of Heredity and Traits" »

1) Physical Barriers Against Infection

Physical barriers are crucial in preventing microbes from reaching susceptible tissues.

Cellular Contributions to Physical Barriers

At the cellular level, tightly joined cells form barriers, preventing invaders from penetrating deeper tissues.

Microbial Evasion of Physical Barriers

Pathogens may use enzymes like proteases to damage physical barriers and gain entry.

2) Layers of Human Skin

Human skin has three layers:

1. Epidermis: Outer layer containing keratin (prevents microbial entry).

2. Dermis: Middle layer with hair follicles, sweat glands, nerves, and blood vessels.

3. Hypodermis: Inner layer with fatty tissue, blood, and lymph vessels.

Significance of Keratin, Fatty Acids, and Skin Shedding

• Keratin: Tough,

Plant Adaptations for Terrestrial Life

Life on land presents unique challenges for plants, requiring specialized adaptations to thrive.

Water Availability Challenges

• Adaptation: Plants have developed root systems to anchor them in the soil and absorb water.
• Example: Cacti have deep roots and can store water in their stems, enabling survival in arid environments.

Overcoming Gravity

• Adaptation: Plants need to support their own weight. They have evolved lignin in their cell walls to provide structural support.
• Example: Trees have thick, woody trunks to support their height and extensive canopy.

Temperature Fluctuations

• Adaptation: Plants have adapted to different climates and varying temperatures.
• Example: Deciduous trees shed their leaves in winter to

The cell is the basic unit of which they are made all living things. It is the smallest unit capable of performing all the functions that characterize a living being.

Depending on whether a body is formed by one or more cells can be:

Unicellular organisms. They consist of a single cell that performs all the functions necessary for survival. Sometimes, several single-celled organisms living together colonies. (like amoeba)

Multicellular organisms. Consist of multiple cells that lose the ability to survive alone. Each cell performs a specific task, and all work together to survive the body (such as plants and animals). Our body is composed of a large number of cells. People are multicellular beings.

The cells in our body can have different shape... Continue reading "The cell, the respiratory system, the organelles, gases, diffusion, active transport ..." »

Nervous System Anatomy

• Functions:

  • Controls perception (sight, touch, hearing, taste).
  • Maintains homeostasis (e.g., blood pressure, body temperature).

• Divisions:

  • Central Nervous System (CNS): Brain & spinal cord (processes information and sends responses).
  • Peripheral Nervous System (PNS): Motor & sensory neurons connecting the CNS to the rest of the body.

• PNS Subdivisions:

  • Somatic Nervous System: Controls voluntary movement (e.g., moving hands).
  • Autonomic Nervous System: Controls involuntary functions (e.g., heart rate).
    • Sympathetic Division (Fight or Flight): Increases alertness, heart rate, etc.
    • Parasympathetic Division (Rest & Digest): Slows heart rate, promotes digestion, etc.

• Structural Differences (Autonomic):

  • Parasympathetic: Long preganglionic

Number and Quantity Prefixes

• Mono-, Uni- (one):
  • Monodiplopia: Double vision that occurs only in one eye.
  • Unilateral: Confined to one side only.
• Bi-, Di- (two, twice, double):
  • Diplopia: Double vision.
  • Bilateral: Affecting two sides.
• Tri- (three):
  • Trigeminal nerve: The fifth cranial nerve, providing sensory innervation to the face, divided into three main branches.
• Quad-, Quadra-, Tetra- (four):
  • Quadrant: Areas divided for descriptive purposes into quadrants.
  • Tetradactyl: Having four fingers or toes on a hand or foot.
• Multi- (many):
  • Multicellular: Composed of many cells.
• Poly- (too much, many):
  • Polyuria: Excessive excretion of urine.
• Hemi-, Semi- (half or partly):
  • Hemiplegia: Paralysis of one side of the body.
  • Semicomatose: State of drowsiness and inaction, requiring