Animal Organization and Homeostasis Chapter 31 BIOL 1000

Animal Organization and Homeostasis Chapter 31 BIOL 1000 Dr. Mohamad H. Termos

Objectives After this lecture you should be able to: - Define tissue - Define extra-cellular matrix - Differentiate between tissue types. - List Tissue classification, general location and function. - Integumentary System - Homeostasis

Tissues are groups of similar cells that work together to provide different structural and/or functional properties to the organ they form. There are four main tissue types which in turn are made up of different forms of tissues. These are: 1 - Epithelial Tissue, 2 - Connective Tissue, 3 - Muscle Tissue, and 4 - Nervous Tissue

Extra-cellular Matrix One of the major differences between tissues is the extracellular matrix, which is a material between cells in tissue, made up of water and a variety of proteins. Some ECM has high content of structural protein fibers that make them flexible or elastic. Some contain many mineral crystals that make them rigid. Others are very fluid.

Epithelial Tissue - Creates the inner and outer linings of organs, - Lines the internal body cavities and the body spaces that open to the external environment. - Forms all exocrine and most endocrine glands.

Characteristics of Epithelial Tissue - Cellularity: composed almost entirely of cells - Polarity: Apical Surface (could be free or top surface), intercellular junctions, and basal surface (that could be fixed or bottom surface). - Attachment: The basal surface of an epithelium is bound to a thin basement membrane. - Avascularity: lack blood vessels - Innervation: some epithelia are richly innervated to detect changes in the environment at the body or organ surface. Most nervous tissue is in the underlying connective tissue. - Regeneration capacity: able to replace damaged epithelia

Functions of Epithelial Tissue - Protection, e. g. Skin that protects the body from mechanical and chemical injury and also from invading bacteria - Sensory functions, found in the skin, nose, eye, and ear. - Secretion, glandular epithelium; secrete hormones, mucus, digestive juices, and sweat. - Absorption, epithelium lining the gut and respiratory tract allows for absorption of nutrients and gas exchange respectively. - Excretion, epithelial lining of kidney tubules

Classification Some epithelia are simple while others are stratified. Simple epithelia are made up of one layer of cells whereas, stratified ones are multilayered. - Simple squamous epithelium - Simple cuboidal - Simple columnar - Pseudo-stratified columnar - Stratified squamous - Stratified cuboidal - Stratified transitional - Glandular epithelium

Simple Epithelium Tissues Simple squamous (e. g. cheek cells): Consists of only one layer of flat cells. Substances can diffuse out through this type of tissue. Simple cuboidal (e. g. kidney tubules): Composed of one layer of cuboidal cells resting on a basement membrane. Looks like single rows of little square boxes with large, round nuclei inside. Simple columnar: Composed of a single layer of elongated cells. Lines the stomach and intestines. Many have modified structures such as goblet cells, cilia and microvilli.

Stratified Epithelial Tissues Stratified squamous (e. g. epidermis of skin): Lines the body surfaces and spaces that are open to the outside environment. Pseudo-stratified Columnar (e. g. respiratory tract linings): At first glance this epithelium looks stratified. But, every cell in it has a connection to the same basement membrane which means it is simple.

Glandular epithelium Epithelium of the glands are specialized for secretory activity. Glands are either exocrine or endcrine - Exocrine glands: secrete their material (e. g sweat) into epithelial surface (e. g skin) via a duct - Endocrine glands: lack ducts and secret their material (e. g hormone) directly to bloodstream.

Connective Tissue - Form the structural elements of organs. - Most abundant and involves various tissue types. - ECM properties are common to all: rich in proteins and proteoglycans. - Functions in protecting, supporting, and binding organs.

Classification of Connective Tissue - Loose connective tissue Dense connective tissue Bone tissue Cartilage Blood

Fibrous Connective Tissue This includes 2 broad categories: - Loose connective tissue: E. g. Adipose tissue. - Dense connective tissue: E. g. Tissues of ligaments, tendons, and skin dermis. The matrix of this type of tissue is rich in collagen.

Loose Connective Tissue: Adipose Tissue - Commonly located beneath the skin (in the hypodermis layer). - Functions in energy storage, organ insulation and protection

Bone - The easiest tissue to identify beside adipose tissue - Mature bone cells are embedded in a matrix material which contains collagen fibers and mineral salt crystals (the latter is responsible for the hardness of the bone)

Bone functions - Provide support and protection for the body - Serve as points of attachment for muscles.

Cartilage - Soft supportive type of connective tissue - Form the soft structures of the nose, and outer ear. - Provides soft support for most of the respiratory tract. - Also found at the end of and between moving bones.

Cartilage Major Classes of cartilages: Hyaline cartilage: the most common. Matrix with low content of collagen. Cover ends of bones that articulate at joints.

Cartilage Fibrocartilage: strongest and most durable. Matrix is rigid and filled with strong collagen. Form intervertebral disks, Elastic cartilage: matrix with large numbers of very fine elastic fibers which makes it flexible. E. g. outer ear.

Blood Tissue - The most unusual type of connective tissue - This is because it exists in liquid state. Blood has two fractions: 1 - Matrix, that’s the plasma (liquid fraction). Makes up 55% of whole blood. 2 - Formed elements (or blood cells). Makes up 45% of whole blood. (http: //www. histology-world. com/photomicrographs/blood 1. jpg)

Classification of Blood Cells Erythrocytes: Red blood cells Leukocytes: white blood cells Thrombocytes: platelets.

Blood functions - Transport of respiratory gases (O 2, CO 2) - Transport of nutrients and waste products. - Maintain a constant body temperature. - White blood cells destroy harmful microorganisms

Muscle Tissue Muscle tissue is almost always function to produce motion. Muscle cells shorten when muscle contact, providing a pushing/pulling tension that’s used to move a part of an organ. Muscle tissues are divided into three types: - Skeletal muscle tissue - Smooth muscle tissue - And cardiac muscle tissue

Muscle Tissue Muscle tissue responds to stimulation from the nervous system to contract

Skeletal Muscle Tissue - Long, striated muscle. - Its fibers are multinucleated and they run parallel to each other. - They are bundled by connective tissue to form the final muscle structure. - Its motion is voluntary (contraction can be consciously controlled).

Skeletal Muscle Tissue - These are the muscles attached to the bones of the skeleton, muscles of head and face, tongue and upper third of esophagus.

Cardiac Muscle - Individual cardiac muscle cell is uninucleated (one nucleus) and branched. - Branched ends are joined together by intercalated discs. - They are striated muscles same as the skeletal. - Contraction of this type of muscle is involuntary. - Cardiac muscle fibers form the myocardium, the muscle tissue layer of the heart.

Smooth Muscle - Smooth muscle cells are thin, uninucleated, and tapered (i. e pointy) on the ends. Cells are joined side to form sheets. These sheets form layers of smooth muscle tissue within the walls of internal organs. They are not striated. Like cardiac muscle, smooth muscle contraction is involuntary. Form the muscles of the digestive tract.

Nervous Tissue - This type of tissue forms the electrical communication system of the body. - Composed of: 1 Neurons (nerve cells), and 2 - Neuroglia (supportive structural layers of nerves, spinal cord, and brain)

Neuron The unit of nervous system. Composed of: - Dendrites, which carry nerve signals toward the axons. - Soma, or cell body, - Axon (that transmit the nerve impulses away from the cell body), http: //library. thinkquest. org/J 001619/neuricon. gif

The Integumentary System • Functions of skin – Covers and protects underlying body regions – Regulates body temperature, and – Contains sensory receptors • Skin and its derivatives make up the integumentary system 32

The Integumentary System • Regions of the Skin – Epidermis - Outer, thinner region • Stratified squamous epithelium • New cells are pushed outward, become keratinized, and are sloughed off • Melanocytes produce melanin (pigment) 33

The Integumentary System • Regions of the Skin (cont. ) – Dermis - Deeper and thicker than epidermis • Fibrous connective tissue – Receptors – Nerve fibers – Blood vessels – Subcutaneous Layer Loose, connective tissue located below dermis 34

31. 4 Homeostasis • The organ systems of the human body contribute to homeostasis – The ability of an organism to maintain a relatively constant internal environment • Homeostatic Control – Controlled by hormones and the nervous system – Negative feedback is the primary homeostatic mechanism that keeps a variable close to a set value • Sensor detects change in environment • Regulatory center initiates an action to bring the conditions back to normal 35

Regulation of Body Temperature by Negative Feedback Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Control center sends data to control center 98. 6°F set point directs response to stimulus Sensor Effect Blood vessels dilate; sweat glands secrete. negative feedback and return to normal temperature stimulus above norm al Normal body temperature below nor mal negative feedback and return to normal stimulus Effect Sensor Blood vessels constrict; sweat glands are inactive. directs response to stimulus Control center sends data to control center 98. 6°F set point

Homeostasis • Positive feedback is a mechanism that brings about an even greater change in the same direction – Childbirth process 37

Conclusions In this lecture we learned about tissue, general classification, location and function. And we learned how and why they are considered the next logical level of organization after the cellular level.