Overview
This lecture introduces tissue types in the human body, the basics of histology, and how to identify muscle tissues under a microscope.
Unicellular vs. Multicellular Life
- Amoebas are single-celled organisms that perform all life processes within one cell.
- Multicellular animals have specialized cells grouped into tissues and organs for complex functions.
- Homeostasis is maintained by cells with specific roles in multicellular organisms.
Tissue Types and Structure
- Tissues are groups of similar cells performing a common function; the term means "woven."
- Organs are formed by the combination of two or more tissues; tissue type defines organ function.
- Four primary tissue types: nervous (control/communication), muscle (movement), epithelial (lining/protection), connective (support).
History and Tools of Histology
- Histology is the study of tissues, made possible by the invention of microscopes in the 1590s.
- Anton van Leeuwenhoek advanced microscopy, discovering microorganisms with ~270x magnification.
- Staining techniques allow visualization of tissue and cellular structures under a microscope.
- Early successful stains like carmine (from insects) highlighted structures, leading to breakthroughs in understanding nervous tissue.
Nervous Tissue
- Nervous tissue senses stimuli and transmits electrical impulses throughout the body.
- Two main cell types: neurons (signal transmission) and glial cells (support, insulation, protection).
- Neuron anatomy: cell body (soma), dendrites (receive signals), axon (send signals).
- Nervous tissue forms the brain, spinal cord (central nervous system), and peripheral nerves.
Muscle Tissue Types
- Muscle tissue contracts to produce movement and is well-vascularized.
- Skeletal muscle: voluntary, striated, multiple nuclei, long cylindrical cells, attached to bones.
- Cardiac muscle: involuntary, striated, usually one nucleus, branching cells joined by intercalated discs; only in heart.
- Smooth muscle: involuntary, non-striated, single nucleus, short tapered cells, lines hollow organs and vessels.
Identifying Muscle Tissues
- Skeletal: striations, multi-nucleated, long straight fibers.
- Cardiac: striations, single nucleus, branching cells, intercalated discs.
- Smooth: no striations, single nucleus, closely packed tapered cells.
Key Terms & Definitions
- Histology — the study of tissues.
- Homeostasis — balance of materials and energy within an organism.
- Neuron — nerve cell that transmits impulses.
- Glial cell — support cell in nervous tissue.
- Striation — striped appearance in muscle tissue.
- Intercalated disc — specialized junctions between cardiac muscle cells.
Action Items / Next Steps
- Review how to distinguish the four main tissue types and subtypes of muscle tissue in microscope images.
- If needed, revisit basic cell biology concepts for foundational understanding.