Animal Science

Organelles of the Cells

Structural Organization of an Animal

  • Hierarchy of Biological Organization:

    • Molecule

    • Cell

    • Tissue

    • Organ

    • Organ System

Definition of a Molecule

  • A molecule is the smallest unit into which matter can be divided without the release of electrically charged particles.

    • Composition: A group of two or more atoms held together by attractive forces known as chemical bonds.

Cell Theory

  • Key Principles:

    • All living things are made up of cells.

    • All cells come from pre-existing cells.

    • Cells are the most basic unit of life.

Prokaryotic vs. Eukaryotic Cells

  • Two Basic Types:

    • Prokaryotic Cells:

    • Simple, usually unicellular organisms.

    • Examples: Bacteria.

    • Characteristics: Lack membrane-bound organelles and a nucleus.

    • Eukaryotic Cells:

    • Multicellular organisms, including plants and animals.

    • Characteristics: Have membrane-bound organelles and a membrane-bound nucleus.

Cell Specialization

  • Cells can specialize to function in particular areas of the body.

    • Gene Regulation: Genes are turned on and off in individual cells to perform specific functions.

    • Specialized cells make up tissues, organs, and systems in the body.

Cell Organelles

  • Definition: Cell organelles are small organs that perform specific functions inside the cell.

    • Organelles assist in various cellular processes.

Cilia and Flagella

  • Cilia:

    • Hair-like projections from the membrane that move in unison to propel the cell.

    • Example: Epithelial cells in the respiratory system have cilia to move dust out of the system.

  • Flagella:

    • A thin thread-like structure that allows for locomotion.

    • Example: Sperm cells have flagella to propel themselves in the reproductive system.

Key Cell Organelles and Their Functions

  • Cell Membrane:

    • The outer membrane of the cell.

    • Function: Controls the movement of substances in and out of the cell.

    • Structure: Composed of a double layer of phospholipids.

  • Cytoplasm:

    • Gel-like mixture surrounded by the cell membrane.

    • Function: Helps in movement, reactions, and protection of organelles.

  • Nucleus:

    • Directs cell activities and is protected by the nuclear membrane.

    • Contains genetic material - DNA.

  • Nucleolus:

    • Found inside the nucleus.

    • Function: Contains RNA to build proteins.

    • Process: Nucleolus -> RNA -> Protein.

  • Nuclear Membrane:

    • Surrounds the nucleus and is made of two layers.

    • Openings allow materials to enter and leave the nucleus.

  • Chromosomes:

    • Located in the nucleus.

    • Made of DNA and contain instructions for traits and characteristics.

  • Endoplasmic Reticulum (ER):

    • Smooth ER:

    • Lacks ribosomes.

    • Function: Produces and synthesizes lipids and hormones.

    • Rough ER:

    • Structure: Ribosomes embedded on the surface.

    • Function: Produces and synthesizes proteins.

  • Ribosomes:

    • Each cell contains thousands of ribosomes.

    • Function: Combine to make proteins, found on Rough ER and floating throughout the cell.

  • Mitochondria:

    • Function: Produces energy through chemical reactions breaking down fats and carbohydrates.

    • Regulates the level of water and other materials in the cell.

    • Recycles and decomposes proteins, fats, and carbohydrates.

  • Golgi Apparatus:

    • Function: Packages proteins, moves materials within the cell, and moves materials out of the cell.

  • Lysosomes:

    • Breaks down proteins, fats, and carbohydrates.

    • Transports undigested material to the cell membrane for removal.

    • Note: The cell may die if a lysosome explodes.

  • Vacuoles:

    • Function: Used for storage; assists in digestion and waste removal; contains a water solution.

Functions of the Skeletal System

  • The skeletal system provides structure, support, and the ability to move the body.

Types of Bones

  • Flat Bones:

    • Definition: Plates of bone that are flat, covering broad spaces.

    • Example: Ribs.

  • Long Bones:

    • Definition: Bones that are longer than they are wide.

    • Example: Femur, tibia, humerus.

  • Short Bones:

    • Definition: Cube-shaped bones that are typically bunched with other short bones.

    • Example: Carpus and tarsus.

  • Irregular Bones:

    • Definition: Bones with complex shapes, unique to specific bones.

    • Example: Vertebrae.

  • Sesamoid Bones:

    • Definition: Small, seed-shaped bones found in tendons.

Functions of Bones

  • Storage:

    • Bones serve as storage houses for fats, blood cells, calcium, phosphorus, magnesium, and amino acids like glycine and proline.

  • Bone Growth and Types:

    • Continuous Growth: Bones continue to grow and develop throughout the organism's life.

    • Osteogenesis: Formation of bone tissue; ossified: hardening of bone from cartilage over time.

Types of Bone Cells

  • Osteoblasts: Form new bone cells.

  • Osteocytes: Maintain and remodel bone cells.

  • Osteoclasts: Break down bone cells and reabsorb proteins and collagen, assisting in bone strength.

Ossification (How Bones Form)

  • Early connective tissue becomes covered in nutrient-rich blood.

  • Osteoblasts begin forming bone by removing calcium from the blood, which hardens together with the osteoblasts forming cartilage.

  • Spongy bone begins to form, followed by the formation of compact bone over the spongy bone.

  • Calcium continues to be deposited as blood vessels and nerves are incorporated.

  • Osteoclasts remove bone as it is broken down, keeping the skeleton dynamic.

Structure of the Skeletal System

  • Bones and cartilage provide overall body structure.

  • Factors Affecting Structure:

    • Bone length

    • Bone thickness

    • Shape

    • Specific number of bones in the body:

    • 206 bones in humans

    • 321 bones in dogs

    • 244 bones in cats

    • 124 bones in hamsters

    • 204 bones in horses

Body Movement

  • Connections between muscles, bones, and joints allow for body movement.

  • Placement and positioning of bones impact movement.

    • Types of Movement:

    • Plantigrade: Walking on the soles of feet or palms (e.g., humans, bears).

    • Digitigrade: Walking on the toes or fingers (e.g., cats, dogs).

    • Ungulgrade: Walking on the fingernails or toenails (e.g., horses, cows, pigs).

Protection of Internal Organs

  • Ribs provide protection and support for the thoracic cavity.

  • Skull protects the brain.

  • Spinal column supports abdominal organs.

Blood Cell Production

  • Red blood cells are produced in the spongy part of bones (bone marrow).

  • Lack of bone marrow can lead to anemia and serious health issues.

Comparative Anatomy

  • The study of similarities and differences in anatomical structures of different animals.

  • It examines bones, muscles, organs, and systems across species.

  • Purpose:

    • Helps understand evolutionary relationships and reveals common ancestors.

    • Shows how different animals adapt to their environments through structural changes.

Types of Skeletons

  • Appendicular Skeleton: Comprises bones that make up the shoulder, face, limbs, pelvis, and hind limbs; primarily for movement and locomotion.

  • Axial Skeleton: Includes bones of the head and trunk, including the vertebrae and ribs; primarily for the protection of internal organs.

  • Fontanel: The soft spot on the top of the skull, made of uncalcified bone at birth; solidifies after birth.

  • Thorax: The part of the body housing the heart and lungs, located between the neck and diaphragm.

Functions of the Skeletal System (Summarized)

  1. Body structure and support.

  2. Movement of the body in connection with the muscular system.

  3. Protection of internal organs, especially in the thoracic cavity.

  4. Production of blood cells.

  5. Storage of nutrients, energy, and minerals, such as calcium, phosphorus, and fat.