Animal Cell Structure and Function

Laboratory II Overview

  • Today's lab objectives:

    • Identify structures and functions of an animal cell.

    • Identify different types of epithelial tissue under the microscope.

Review from Lab 1

  • Key concepts to know:

    • Anatomical position

    • Directional terms

    • Body planes

    • Body cavities (including the 3 thoracic sub-cavities as detailed in the manual)

    • Organs identified as Cosmo's organs:

    • Brain

    • Spinal cord

    • Heart

    • Lungs

    • Urinary bladder

    • Kidneys

    • Large intestine (LI)

    • Pancreas

    • Small intestine (SI)

    • Stomach

    • Liver

    • Gallbladder

    • Spleen

    • 4 quadrants of the abdominal cavity

    • Organ system table (components/functions related to different organ systems)

    • Parts of the microscope (essential for lab practice)

Components of a Cell

  • Three main components:

    • Plasma membrane:

    • Description: The selectively permeable outer barrier of the cell.

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

    • Nucleus:

    • Description: The control center of the cell.

    • Function: Contains genetic material (DNA) that governs cellular structure and function.

    • Cytoplasm:

    • Description: Everything inside the cell excluding the nucleus.

    • Components:

      • Cytosol: The fluid inside the cell.

      • Organelles: Subcellular structures that perform various functions within the cell, described as "little organs".

Cellular Structures and Their Functions

  • Different cellular structures include:

    • Plasma membrane: Selectively permeable (outer barrier).

    • Nucleus: Contains DNA, regulates cell functions.

    • Nucleolus:

    • Function: Responsible for ribosome production.

    • Ribosome:

    • Function: Site of protein synthesis.

    • Cytosol:

    • Function: Fluid filling the cytoplasm around organelles.

    • Rough endoplasmic reticulum (RER):

    • Function: Synthesizes glycoproteins and phospholipids; has ribosomes attached for protein synthesis.

    • Smooth endoplasmic reticulum (SER):

    • Function: Synthesizes lipids (fatty acids and steroids).

    • Golgi apparatus (Golgi body/Golgi complex):

    • Function: Modifies, sorts, packages, and transports proteins from the RER.

    • Mitochondrion:

    • Function: Generates energy (ATP), termed the "powerhouse" of the cell.

    • Lysosome:

    • Function: Contains digestive enzymes for breaking down various molecules.

    • Centrioles:

    • Function: Organizing center for mitotic spindles (essential for cell division).

    • Cytoskeleton:

    • Description: A network of protein filaments extending through the cytosol.

    • Note: Not usually seen on models but is crucial for cell shape and movement.

Identification Skills for Practical Exam

  • In the practical, students will need to:

    • Be aware of the function assigned to a structure and identify the related cellular structure.

Definition of Tissues

  • Tissues: Groups of cells working collectively to perform specialized activities.

Four Types of Tissues

  1. Epithelial Tissue:

    • Description: Covers body surfaces, lines hollow organs, and forms glandular tissues.

  2. Connective Tissue:

    • Description: Provides support and protection for other tissues.

  3. Muscle Tissue:

    • Description: Responsible for movement in various forms.

  4. Nervous Tissue:

    • Description: Facilitates communication and control among different body parts.

Characteristics of Epithelial Tissues

  • Noteworthy characteristics include:

    • Excellent barrier properties due to closely packed cells.

    • Basal surface (attached to deeper tissue) and apical surface (exposed to the environment).

    • Avascular (lack of blood vessels).

    • Innervated (connects to the nervous system).

    • Regenerative (dead or worn-out cells are continually replaced).

    • Functions include protection, filtration, absorption, secretion, and excretion.

Types of Epithelial Tissues: Layers and Shapes

  • Classifications by layers include:

    • Simple:

    • Single layer of cells.

    • Stratified:

    • Multiple layers of cells.

    • Pseudostratified:

    • Appears layered due to varying cell heights but is a single layer with all cells attached to the basement membrane.

  • Classifications by shapes include:

    • Squamous: Flat cells.

    • Cuboidal: Cube-shaped cells.

    • Columnar: Column-like cells.

Detailed Descriptions of Simple Epithelium

  • 1. Simple Squamous Epithelium:

    • Structure: Single layer of flat cells with a centrally located nucleus.

    • Function: Filtration, diffusion, rapid exchange of materials.

    • Locations: Air sacs of lungs, kidney filtration membranes, lining of blood vessels, and serous membranes.

  • 2. Simple Cuboidal Epithelium:

    • Structure: Single layer of cube-shaped cells with a centrally located nucleus.

    • Function: Secretion.

    • Locations: Kidney tubules, glands.

  • 3. Simple Columnar Epithelium:

    • Structure: Single layer of column-like cells (ciliated or non-ciliated).

    • Functions: Secretion, absorption.

    • Features: May contain cilia, goblet cells (mucus secretion), and microvilli (increased surface area for absorption).

    • Locations: Lining of spinal cord and brain (ciliated), GI tract (non-ciliated), kidney ducts (non-ciliated).

  • 4. Pseudostratified Columnar Epithelium:

    • Structure: Appears layered due to different nuclei levels but all are attached to the basement membrane.

    • Function: Secretion; can be ciliated or non-ciliated.

    • Location: Mainly found in the respiratory tract.

Detailed Descriptions of Stratified Epithelium

  • 1. Stratified Squamous Epithelium:

    • Structure: Several layers of cells, with deeper layers being polymorphic cells, and several layers of squamous cells forming the apical layer. Can be keratinized or non-keratinized.

    • Function: Provides protection against abrasion, water loss, UV radiation; serves as the first line of defense against microbial invasion.

    • Locations: Keratinized type found in the epidermis (superficial layer of skin); non-keratinized type lines wet surfaces like the mouth and esophagus.

  • 2. Transitional Epithelium:

    • Structure: Cells in the apical layer appear variable in shape (squamous when stretched, cuboidal when relaxed).

    • Function: Allows for stretching to accommodate changes in volume.

    • Locations: Lines portions of the urinary system, such as the urinary bladder.

Practical Application for Identification

  • Students must be able to:

    • Identify epithelial tissues by picture and describe their function/location during the practical examination.