Cells and Tissues: Foundations of Human Anatomy and Physiology

Topic 2: Cells and Tissues

Introduction

This topic explores the fundamental building blocks of the human body: cells and tissues. Understanding their structure and function is essential for comprehending how the body operates at both microscopic and macroscopic levels.

Review of Key Concepts

• Anatomy is the study of the structure of body parts and their relationships to one another.

• Physiology is the study of the function of the body’s structural machinery.

• Gross anatomy refers to the study of structures visible to the naked eye.

• Histology is the study of tissues.

• Cytology is the study of cells.

Topic 1 Review Questions

• What is the difference between anatomy and physiology? Anatomy focuses on structure, while physiology focuses on function.

• Gross anatomy is the study of structures visible to the naked eye.

• The study of tissues is called histology.

• To analyze the metabolic activity of tissues in the body, you would use what kind of radiographic technique? Positron Emission Tomography (PET) or functional MRI (fMRI) are commonly used.

• Name one structure located in the thoracic cavity: Heart or lungs.

• A serous membrane has two layers.

• The ______ membrane surrounds the lungs: Pleural membrane.

• Name one structure located in the right hypochondriac region of the abdomen: Liver or gallbladder.

Microscopic Anatomy: Cytology vs. Histology

Microscopic anatomy involves the study of structures that cannot be seen without magnification. It is divided into two main branches:

• Cytology: The study of individual cells and their internal structures.

• Histology: The study of tissues, which are groups of similar cells performing a common function.

For example, a cardiac muscle cell is a single cell, while cardiac muscle tissue is composed of many such cells working together.

Cells and Their Environment

Definitions

• Intracellular materials: Substances found within cells, including cytoplasm, organelles, and inclusions (e.g., hemoglobin, glycogen, keratin).

• Extracellular materials: Substances found outside cells, in the spaces between cells in a tissue or in body cavities. Also called intercellular material.

Multicellular organisms include cells that are located in a range of chemical environments, both inside and outside the cell.

Tissue Culture

Tissue culture is a laboratory technique in which cells are grown under controlled conditions, usually outside their natural environment. This allows for the study of cell behavior, drug testing, and genetic research.

• Applications: Cancer research, vaccine production, genetic engineering, and regenerative medicine.

• Example: Growing cardiac muscle cells in culture to study heart disease.

Serous Membranes

Serous membranes are thin, double-layered membranes that line body cavities and cover organs. Each has two layers:

• Parietal layer: Lines the cavity wall.

• Visceral layer: Covers the organ itself.

Examples include the pleural membrane (lungs), pericardial membrane (heart), and peritoneal membrane (abdominal organs).

Summary Table: Intracellular vs. Extracellular Materials

Type	Location	Examples
Intracellular	Inside the cell	Cytoplasm, organelles, hemoglobin, glycogen
Extracellular (Intercellular)	Between cells or in body cavities	Interstitial fluid, plasma, extracellular matrix

Additional info:

• Radiographic techniques such as PET and fMRI are used to study tissue metabolism and function.

• The right hypochondriac region is one of nine regions used to describe locations in the abdomen.