BIOL122 tissue type and structure

What is the definition of a tissue?

A group of similar cells that usually share a common embryonic origin and function together to perform specialized functions

What are the four basic tissue types in the human body?

1. Epithelial tissue 2. Connective tissue 3. Muscle tissue 4. Nervous tissue

Match the 3 embryonic germ layers (Endoderm, Mesoderm, Ectoderm) to the tissues they form.

• Endoderm (Inside): Epithelial cells.

• Mesoderm (Middle): Connective tissue, muscle tissue, and epithelial cells.

• Ectoderm (Outside): Nervous tissue and epithelial cells.

What are the 5 main types of cell junctions?

a) Tight junctions

• b) Adherens junctions

• c) Desmosomes

• d) Hemidesmosomes

• e) Gap junctions

What is the key characteristic/function of a Tight Junction?

It forms tight seals between adjacent plasma membranes to prevent fluid leakage.

What is the key characteristic/function of an Adherens Junction?

It provides structural strength using an adhesion belt, microfilaments (actin), and transmembrane glycoproteins (cadherin).

What is the key characteristic/function of a Desmosome?

It allows tissues to withstand intense mechanical stress by linking adjacent cells via intermediate filaments (keratin) and plaque.

What is the key characteristic/function of a Hemidesmosome?

It anchors cells securely to the extracellular matrix / basement membrane using integrin proteins.

What is the key characteristic/function of a Gap Junction?

It forms narrow gaps/tunnels (using connexon proteins) that allow rapid electrical or chemical exchange between cells.

What is the primary role of Nervous Tissue?

It detects internal and external changes in body conditions and acts to maintain homeostasis.

Name the two main cell types found in nervous tissue and their primary jobs.

1. Neurons: Generate and conduct nerve impulses. 2. Neuroglia: Non-conducting cells that insulate, support, and protect neurons.

What are the three primary structural regions of a neuron?

1. Cell Body: Contains the nucleus and other vital organelles.

2. Dendrites: Receive incoming signals.

3. Axons: Conduct signals over long distances.

What is the primary role of Muscle Tissue?

It generates physical force required for movement.

Describe the features, control, and location of Skeletal Muscle.

Features: Long, cylindrical, parallel fibers; striated appearance; contains many peripheral nuclei.

• Control: Voluntary (conscious control).

• Location: Attached to the bones of the skeleton.

Describe the features, control, and location of Cardiac Muscle.

Features: Striated; central nuclei; cells are uniquely joined end-to-end via intercalated discs.

Control: Involuntary.

Location: Found exclusively in the walls of the heart.

Describe the features, control, and location of Smooth Muscle.

Features: Non-striated; spindle-shaped cells (thick in the middle, tapered at ends); single central nucleus; cells are connected by gap junctions in areas like the intestines.

Control: Involuntary.

Location: Walls of hollow internal structures (e.g., blood vessels, lung airways, intestines).

What are the general structural characteristics of Epithelial Tissue?

Forms continuous sheets.

• Avascular (lacks blood vessels) but innervated (has nerves).

• High proliferative potential (high rate of cell division for rapid repair).

Function and Location of Simple Squamous Epithelium?

Function: Filtration or gas/fluid exchange via diffusion.

Location: Kidneys, capillaries, lung alveoli, lymphatic vessels.

Function and Location of Simple Cuboidal Epithelium?

Function: Secretion and absorption.

Location: Kidney tubules, small glands.

Function and Location of Simple Columnar Epithelium (Non-ciliated vs. Ciliated)?

Non-ciliated: Functions in absorption & secretion; located in the digestive tract, gallbladder, and some excretory glands.

Ciliated: Functions to move mucus or cells; located in the upper respiratory tract (moves mucus) and fallopian tubes (moves eggs).

Function and Location of Stratified Squamous Epithelium?

Function: Protection from physical abrasion.

• Location: Oesophagus (non-keratinized) and epidermis of the skin (keratinized).

Function and Location of Stratified Cuboidal & Stratified Columnar Epithelium?

Stratified Cuboidal: Protection, secretion, and absorption; located in the large ducts of glands.

• Stratified Columnar: Protection and secretion; located in the urethra and ducts of some large glands (like salivary glands).

Function and Location of Transitional Epithelium?

Function: Permits distension (stretching).

• Location: Urinary bladder and ureters.