Lecture Slides-Animal Structure and Function

5 x 1013 why are cells so small and why do we have so

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 75 trillion cells (7.5 x 1013) Why are Cells So Small and Why Do We Have So Many? • There are ~ 1 billion cells per gram of tissue (109 cells/g) assuming nominal human male weight of 70 kg • Small cells maximize surface area to volume ratio • Variability between cells is minimized by having very large numbers • Statistical variability (s.d.) approx. by √N • For 1 g of tissue: √N = √109 = 3.2 x 104 Relative error = √N/N = .003% Relative Tissues, Organs, and Organ Systems • Epithelial tissues are sheets of tightly connected cells that cover body surfaces and line hollow organs. • Connective tissues support and reinforce other tissues. They generally consist of dispersed cells in an extracellular matrix. • Muscle tissues contract. There are three types: skeletal, cardiac, and smooth. • There are two types of cells in nervous tissues: Neurons generate and transmit electrochemical signals, and glial cells provide supporting functions for neurons. Epithelial Tissues • EPITHELIAL TISSUES are sheets of interconnected cells that cover the body surfaces and line hollow internal b...
View Full Document

This note was uploaded on 10/25/2010 for the course MUS 347 taught by Professor Mook during the Fall '08 term at ASU.

Ask a homework question - tutors are online