3.1 Cells and Tissues Page 85 – 92

3.1 Cells and Tissues (Page 85) Most of the 75-100 trillion cells that make up the human body are specialized to do certain tasks. The three main factors that influence the differentiation of these cells are: the contents of the cell’s cytoplasm environmental conditions, such as temperature the influence of neighbouring cells Copyright © 2010 McGraw-Hill Ryerson Ltd.

Cell Specialization: Cytoplasm Content (Page 85) Differences between the cells in an amoeba and cells in a blue whale are related to differences in cytoplasm content. The process of mitosis ensures that each daughter call receives identical sets of chromosomes. The cytoplasm can be different in each daughter cell. Many cells – and how they will specialize has already been determined, this early specialization is partly because of differences in a cells cytoplasm. Example: One daughter cell might have more storage vacuoles than the other. Having more of these vacuoles will let the cell to use more energy as it grows. Copyright © 2010 McGraw-Hill Ryerson Ltd.

Cell Specialization: Environmental Conditions (Page 86) Environmental conditions play a large role in cell specialization Environmental factors include: 1. temperature 2. presence or absence of nutrients Differences in environment can explain why cells with identical genes will develop differently Example: Siamese cats, only cells that develop at cool temperatures produce dark hair colours. On the cat pictured below, dark- and light-coloured hair developed when skin cells experienced warm or cool temperatures during cell differentiation. Copyright © 2010 McGraw-Hill Ryerson Ltd.

Cell Specialization: Neighbouring Cells (Page 86) Nearby cells in the organism’s body have one of the biggest influences on what a cell will become. When cells are close to one another, the substances produced by one cell can diffuse through a neighbouring cell’s membrane. These substances can then change the information of the DNA of the second cell gets expressed. In this chick embryo, neighbouring cells influence the development of the eye in a specific location. Copyright © 2010 McGraw-Hill Ryerson Ltd.

Cell Specialization: Abnormal Cell Development (Page 87) Chemical contaminants in the environment have also been shown to trigger abnormal development. In humans, about 90% of problems in developing embryos can be traced to environmental factors. Example: A mother’s exposure to heavy metals. As a cell matures, some genes get turned off or on by the effects of other cells or environmental conditions. One combination of active and inactive genes will produce a muscle cell, or a nerve cell. A cell with similar conditions become specialized to do similar jobs. The production of abnormal cells is often linked to environmental conditions, such as the presence of chemical contaminants, temperature changes, diseases, and parasites, that are present during cell development. Similar cell conditions form similar cells. Copyright © 2010 McGraw-Hill Ryerson Ltd.

Types of Tissues (Page 88) Tissue: a cluster of similar cells that share the same specialized structure and function. There are only four main types of tissue: epithelial, muscle, nervous, and connective. Epithelial Tissue Copyright © 2010 McGraw-Hill Ryerson Ltd.

Types of Tissues Muscle Tissue (Page 88) Copyright © 2010 McGraw-Hill Ryerson Ltd.

Types of Tissues Nervous Tissue (Page 89) Copyright © 2010 McGraw-Hill Ryerson Ltd.

Types of Tissues Connective Tissue (Page 89) Copyright © 2010 McGraw-Hill Ryerson Ltd.

Stem Cells (Page 90) Stem Cell: an unspecialized cell that can produce various specialized cells Copyright © 2010 McGraw-Hill Ryerson Ltd.

Stem Cells Early in their development, human embryos have totipotent stem cells. Totipotent stem cells – can become any type of cell in the body As the embyos develops, its stem cells become pluripotent. Pluripotent – These cells are less versatile, they can produce many but not all types of cells. Late in development after birth, people only have adult stem cells, which can only produce specific kinds of cells. Example: Only skin stem cells can produce cells to repair skin, and only bone stem cells can repair bone.

Uses of Stem Cells (Page 91) Embryonic stem cells (totipotent stem cells) are unspecialized cells that can become any one of an organism’s body cells, making them valuable for research and medical treatment. Copyright © 2010 McGraw-Hill Ryerson Ltd.

Concepts to be reviewed: Section 3.1 Review (Page 92) Concepts to be reviewed: the factors affecting cell specialization (cytoplasm contents, environmental factors, and neighbouring cell secretions) the four types of tissues (muscle, epithelial, nervous, and connective) the potential and ethical concerns over the production or harvesting of stem cells Homework  Read pages 85 to 91 Complete page 90 #1-4 and page 92 #2-6, 8 Copyright © 2010 McGraw-Hill Ryerson Ltd.