Chapter 3: Cells and Tissues. I. Overview of the Cellular Basis of Life A. Cells are the building blocks of all living things . The human body has 50 to 60 trillion of these tiny building blocks. B. Cells carry out all chemical activities needed to sustain life.
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I. Overview of the Cellular Basis of Life
A. Cells are the building blocks of all living things. The human body has 50 to 60 trillion of these tiny building blocks.
B. Cells carry out all chemical activities needed to sustain life.
C. Our cells are made of four primary elements- carbon, hydrogen, oxygen and nitrogen
D. 60% of our cells are made of water (one reason it is essential for life)
E. Cells of the body are constantly bathed in a dilute saltwater solution called interstitial fluid.
1. All exchanges between cells and blood are made through interstitial fluid.
F. Cells vary dramatically in the functions they play within the body.
A. Cells are organized into three main regions
a. contains DNA (genetic
3. Plasma Membrane
a. barrier for cells contents
b. double phospholipids bilayer
c. Selectively permeable-
regulates what enters leaves
Selective Transport Animations
1. All cells share the same general structures; a cell membrane, a nucleus and cytoplasm. However, their function in the body is different. See examples below:
Secretory vs. Absorptive Epithelial Picture
Thin for gas exchange between alveoli and capillaries
Can secrete mucus and have cilia to help clean air
Contain lots of golgi and ER to manufacture and secrete or absorb
Many layers of cells to replace those lost when swallowing
Adapted for secretion of mucus and ciliated to propel food
Stretches as bladder fills with urine
A. Found everywhere in the body, the most abundant and widely distributed tissue.
B. Functions include: binding tissues together, support, and protection
C. Characteristics of connective tissue:
A. Two types of tissue repair:
1. Tissue regeneration is the replacement of destroyed tissue by the same kind of cells
2. Fibrosis occurs when repair by dense fibrous connective tissue called scar tissue forms. Fibrosis occurs in cardiac and nervous tissues of the body.
B. The type of tissue repair depends on the type of tissue damageand the severity of the injury.
C. Steps in Tissue repair
1. Capillaries become very permeable.
2. Clotting proteins and other substances seep into the injured area.
3. A clot is constructed to wall off the injured area (when the clot dries and hardens this forms the scab).
4. Formation of granulation tissue (delicate tissue that is made of new capillaries that grow into the damaged area).
a. this tissue also contains fibroblasts that synthesize collagen fibers that bride the gap
5. Surface epithelium regenerates; this covers an underlying layer of fibrosis (the scar).
D. The regeneration of tissue
1. Tissues that regenerate easily: epithelial, fibrous connective, and bone
2. Tissues that regenerate poorly: skeletal muscle
3. Tissues that are replaced largely with scar tissue: cardiac and nervous tissue within the brain and spinal cord. Scar tissue lacks the normal flexibility of tissues which hinders the functioning.
E. As we age there is a decrease in mass and viability of most tissues. The epithelia thin, the amount of collagen in the body declines which makes tissue repair less efficient, and nervous tissues begins to atrophy.