Study Guide: Tissues and Membranes in Anatomy & Physiology

Epithelial Tissue

Definition and Functions

Epithelial tissue is a type of tissue that lines the surfaces and cavities of organs and structures throughout the body. It serves as a protective barrier and is involved in absorption, secretion, and sensation.

• What is it? Epithelial tissue consists of tightly packed cells forming continuous sheets.

• 2 Forms: Simple (single layer) and Stratified (multiple layers).

• 6 Functions: Protection, absorption, filtration, excretion, secretion, and sensory reception.

Structural Features

• Apical Surface: The exposed surface of epithelial cells, often facing a lumen or external environment.

• Basal Surface: The bottom surface attached to the underlying connective tissue via the basal lamina.

• Basal Lamina: A thin supporting sheet that acts as a filter and anchor for epithelial cells.

• Microvilli: Finger-like extensions that increase surface area for absorption.

Support and Nutrition

• Support: Epithelial sheets are supported by connective tissue beneath the basal lamina.

• Blood Vessels: Epithelia are avascular (do not contain blood vessels) and receive nutrients via diffusion from underlying tissues.

• Regeneration: Epithelial tissue has a high regenerative capacity due to rapid cell division.

Classification

• Cell Shapes: Squamous (flat), Cuboidal (cube-shaped), Columnar (tall and column-like).

• Layering: Simple (one layer), Stratified (multiple layers).

Glands

• Endocrine vs. Exocrine: Endocrine glands secrete hormones into the bloodstream; Exocrine glands secrete products into ducts or onto surfaces.

• Unicellular Exocrine Glands: Example: Goblet cells that secrete mucus.

• Merocrine vs. Holocrine: Merocrine glands release products by exocytosis; Holocrine glands release products when cells rupture.

Connective Tissue

Characteristics

Connective tissue supports, binds, and protects other tissues and organs. It is the most abundant and widely distributed tissue type.

• 3 Characteristics: All connective tissues have cells, fibers, and ground substance.

• Ground Substance: The material that fills the space between cells and fibers; consists of water, proteins, and polysaccharides.

• Fibers: Collagen (strength), Elastic (stretch), Reticular (support).

Types of Connective Tissue

• Loose Connective Tissue (e.g., areolar, adipose)

• Dense Connective Tissue (e.g., tendons, ligaments)

• Specialized Connective Tissue (cartilage, bone, blood)

Cartilage

Composition and Characteristics

Cartilage is a flexible connective tissue found in joints, ear, nose, and respiratory tract.

• Composed of: Chondrocytes (cartilage cells) within a firm matrix of collagen fibers and proteoglycans.

• Characteristics: Avascular, receives nutrients by diffusion.

Bone

Structure and Vascularization

Bone is a rigid connective tissue that forms the skeleton.

• Vascularization: Bone is well vascularized, allowing for nutrient delivery and repair.

• Matrix: Consists of collagen fibers and mineral deposits (mainly calcium phosphate).

Blood

Classification and Function

Blood is a fluid connective tissue that transports nutrients, gases, and wastes.

• Why connective tissue? Blood has cells (red, white, platelets) suspended in plasma (matrix).

• Purpose: Transport, regulation, and protection.

Muscle Tissue

Types and Characteristics

Muscle tissue is responsible for movement and force generation.

• Voluntary Muscles: Skeletal muscle (attached to bones, striated, voluntary).

• Involuntary Muscles: Cardiac muscle (heart, striated, involuntary); Smooth muscle (walls of organs, non-striated, involuntary).

• Locations: Skeletal (bones), Cardiac (heart), Smooth (digestive tract, blood vessels).

Nervous Tissue

Structure and Function

Nervous tissue is specialized for communication via electrical and chemical signals.

• Neuron: The basic cell of nervous tissue, responsible for transmitting impulses.

Covering and Lining Membranes

Types and Locations

Membranes cover body surfaces and line cavities.

• 3 Types: Mucous membranes (line cavities open to exterior), Serous membranes (line closed cavities), Cutaneous membrane (skin).

• Pleura: Serous membrane around lungs.

• Pericardium: Serous membrane around heart.

• Peritoneum: Serous membrane around abdominal organs.

Tissue Repair

Stages of Repair

Tissue repair restores structure and function after injury.

• 3 Stages:

  1. Inflammation – prepares area for repair.

  2. Organization – formation of granulation tissue.

  3. Regeneration/Fibrosis – replacement of tissue or formation of scar.

Regenerative Capacity

Tissue Regeneration

Different tissues have varying abilities to regenerate after injury.

• Greatest Capacity: Epithelial and connective tissues (except cartilage).

• Least Capacity: Cardiac muscle and nervous tissue.

Summary Table: Types of Tissues and Key Features

Tissue Type	Main Function	Regenerative Capacity	Key Features
Epithelial	Protection, absorption, secretion	High	Sheets of cells, avascular, rapid division
Connective	Support, binding, protection	Variable (high in bone, low in cartilage)	Cells, fibers, ground substance
Muscle	Movement	Low (cardiac), moderate (skeletal)	Striated/non-striated, voluntary/involuntary
Nervous	Communication	Very low	Neurons, glial cells