Human Anatomy and Physiology

Posted on Nov 28, 2024 in Biology

Anatomy: the science of body structures and their components; their shape, size, and position.

Physiology: the science that studies the functions of these structures and bodily processes; how body parts work.

Pathology: the branch of medicine that studies diseases, their causes, and manifestations.

Biochemistry: the science that studies biological processes at the molecular level.

2-ANALYSIS OF THE HUMAN BODY’S HIERARCHICAL STRUCTURE

  • The chemical level: atoms and molecules. Atoms and molecules combine to form structures at the cellular level.
  • The cellular level: the basic structural and functional unit.
  • The tissue level: groups of similar cells. There are four basic tissue types: epithelial, connective, muscle, and nervous.
  • The organ level: organs consist of two or more tissue types with specific functions and recognizable forms.
  • The system level: different organs working together. An organ can be part of more than one system.

3-CHEMICAL STRUCTURE, CLASSIFICATION, AND ROLES OF BODY COMPONENTS

Living matter is characterized by its organization and properties, which depend on its composition and molecular structure.

Molecules that form biological materials are called biomolecules, formed by specific elements: bioelements.

Bioelements are classified into three groups by abundance:

  • Primary bioelements: make up 95% of the total mass.
  • Secondary bioelements: constitute about 4.5% of the total mass.
  • Trace elements: present in small amounts but essential; their absence can cause deficiency diseases.

Bioelements combine to form biomolecules, classified into two groups:

  • Inorganic biomolecules: inert materials like water and mineral salts.
  • Organic biomolecules: found only in living matter; the main ones are carbohydrates, lipids, proteins, vitamins, and nucleic acids.

Biomolecules have three main functions:

  • Structural: form biological structures.
  • Energetic: release or store energy.
  • Regulatory: involved in biological reactions.

Water is the most important molecule in living things. Most of our body is water, and it:

  • Dissolves most biomolecules.
  • Buffers temperature changes.
  • Facilitates chemical reactions.

Carbohydrates or sugars are molecules composed of carbon, hydrogen, and oxygen atoms. Sources are:

  • Exogenous: diet (cereals, tubers, etc.).
  • Endogenous: synthesized by the body.

Their functions are:

  • Energy (4 Kcal/g).
  • Structural (protection in plants, fungi, and bacteria).
  • Dietary fiber (like cellulose).

They are classified into:

  • Monosaccharides: simplest carbohydrates with 3 to 7 carbon atoms (ribose, glucose, fructose, galactose).
  • Oligosaccharides: carbohydrates composed of 2 to 10 monosaccharides:
    • Sucrose: glucose + fructose
    • Lactose: galactose + glucose
    • Maltose: glucose + glucose

Lipids or fats are diverse chemical compounds consisting of C, H, and O.

Their functions are:

  • Regulatory
  • Energetic
  • Structural
  • Thermal insulation

They are classified into:

  • Simple: a single molecule (steroids, cholesterol, etc.).
  • Compound: two or more molecules, at least one acting as a lipid (triglycerides, glycolipids, phospholipids, sphingolipids).

Proteins are biomolecules formed by hydrogen, oxygen, nitrogen, and sometimes sulfur, phosphorus, iron, copper, and magnesium.

Proteins are chains of 20 amino acids linked by peptide bonds. Their role is primarily structural, forming the building blocks of living matter.

Vitamins are various organic compounds essential for maintaining vital body functions. They can act as coenzymes, antioxidants, or hormones.

Common characteristics of vitamins:

  • Organic compounds containing carbon, hydrogen, and sometimes oxygen, nitrogen, and sulfur.
  • Do not participate in structure formation; they are acalorific nutrients.
  • Partial (hypovitaminosis) or total (VAD) deficiency is possible.
  • Excess vitamin intake (hypervitaminosis) can occur.

Vitamins are classified by solubility:

  • Water-soluble vitamins (B and C)
  • Fat-soluble vitamins (A, D, E, and K)

Nucleic acids are large molecules composed of long chains of nucleotides. A nucleotide consists of:

  • A pentose
  • Phosphoric acid
  • A nitrogenous base

There are two types of nucleic acids:

  • DNA (double-stranded)
  • RNA (single-stranded)

4-STRUCTURE AND FUNCTION OF THE CELL

The cell is the basic structural and functional unit of living organisms. It is composed of coordinated parts that perform unique structural and biochemical functions.

Cells are classified into two groups:

  • Prokaryotes: lack a nuclear membrane; genetic material is dispersed in the cytoplasm. Example: bacteria.
  • Eukaryotes: have a nuclear membrane surrounding their genetic material; they are larger than prokaryotes and contain organelles. Plants and animals are composed of eukaryotic cells.

Cell anatomy

Eukaryotic cells consist of three main parts: the cell membrane, cytoplasm, and nucleus.

The cell membrane is a flexible casing surrounding the cell, formed by a lipid bilayer with embedded proteins. Some cells have cilia or flagella. It acts as a barrier regulating the flow of substances into and out of the cell.

The nucleus is a spherical or oval organelle enclosed by a nuclear membrane. Most cells have a single nucleus, but some (like mature red blood cells) have none, and others (like skeletal muscle cells) have multiple nuclei. The nucleus contains nucleoli and genes arranged along chromosomes. Genes control nuclear structure and most cell activities.

The cytoplasm is the material between the cell membrane and the nuclear membrane. It consists of cytosol, the cytoskeleton, and organelles.

  • Cytosol: the liquid portion of the cytoplasm, composed of water with dissolved and suspended particles.
  • Cytoskeleton: a network of protein fibers that maintains cell shape.
  • Organelles:
    • Ribosomes: membrane-less globular structures.
    • Endoplasmic reticulum: a membrane system of cisterns, vesicles, and tubules throughout the cytoplasm.
    • Golgi apparatus: a stack of flattened vesicles involved in protein transport, maturation, sorting, and delivery.
    • Mitochondria: structures that oxidize organic matter to obtain energy (the cell’s powerhouses).
    • Vacuoles: membrane-bound vesicles containing water.
    • Centrosome: found in animal cells; organizes microtubules.
    • Lysosomes: vesicles containing digestive enzymes; digest organic material.

Cell physiology

Cells carry out chemical reactions to stay alive: nutrition, relation, and reproduction.

Nutrition: obtaining raw materials and energy through metabolic reactions.

Relation: responding to external stimuli (chemical, light, and acoustic) to adapt to the environment.

Reproduction: cell division resulting in two daughter cells:

  • Mitosis: produces identical daughter cells.
  • Meiosis: a more complex process producing daughter cells with half the genetic information; involved in sexual reproduction.

5-TISSUES

Tissues are groups of cells arranged to perform a specific function. They are intermediate between cells and organs.

Tissues consist of cells and a matrix, important for tissue structure and function. Cells within a tissue can differ morphologically (shape and size) and physiologically (function). Some tissues transport materials, others contract to produce movement, and others secrete hormones.

Body tissues are classified into four basic types: epithelial, connective, muscle, and nervous.

Epithelial tissue covers external surfaces (skin) or internal surfaces (mucosa). Its roles include providing a protective barrier, transporting materials, absorbing substances, and synthesizing useful substances.

There are two types:

  • Covering epithelium: forms the epidermis, outer coverings of some viscera, and linings of blood vessels and respiratory, digestive, urinary, and reproductive systems. It is classified by cell arrangement and shape:
    • Simple: a single layer of cells:
      • Squamous: flattened cells; allow rapid transport of substances.
      • Cuboidal: cube-shaped cells; involved in secretion or absorption.
      • Columnar: tall, cylindrical cells; provide protection to underlying tissues; may be ciliated.
    • Stratified: two or more layers of cells.
    • Pseudostratified: a single layer of cells appearing as multiple layers due to varying nuclear heights.
  • Glandular epithelium: secretes substances; consists of specialized epithelial cells. It is classified as:
    • Exocrine: glands with ducts that expel substances externally.
    • Endocrine: ductless glands that release substances into the bloodstream.

Connective tissue is the most abundant and widely distributed tissue in the body. It connects, supports, strengthens, protects, and insulates other tissues and organs.

Connective tissues include loose connective tissue, dense connective tissue, adipose tissue, bone, cartilage, and blood.

  • Loose connective tissue: many cells and interwoven fibers.
  • Dense connective tissue: numerous thick fibers and fewer cells.
  • Adipose tissue: contains adipocytes that store fat.
  • Bone tissue: the main component of bones.
  • Cartilage: supports other tissues; found in the skeleton, joints, ears, nose, and larynx.
  • Blood: a liquid matrix (plasma) with cells and no fibers.

Muscle tissue consists of cells (muscle fibers) that generate force to produce movement, maintain posture, and generate heat.

There are three types of muscle tissue:

  • Striated muscle tissue (skeletal): voluntary contraction; moves the skeleton.
  • Smooth muscle tissue: found in the walls of hollow viscera (gastrointestinal tract, bronchi, bladder, blood vessels); involuntary contraction.
  • Cardiac muscle tissue: forms most of the heart wall; involuntary contraction.

Nervous tissue consists of neurons and neuroglia. Neurons generate and transmit nerve impulses. Neuroglia surround, protect, and nourish neurons. Nervous tissue forms the central and peripheral nervous systems.