Vertebrate Tissues

Differentiation

The embryonic stage begins on the 15th day after conception and continues until about the 8th week During this period the cells of the embryo are not only multiplying, but they are taking on specific functions. This process is called tissue differentiation. It is during this critical period of differentiation that the growing fetus is most susceptible to damage from external sources (teratogens) including viral infections such as rubella, x- rays and other radiation, and poor nutrition.

Tissue Group of cells that carry out a specific function.

4 Basic Tissue Types Epithelial Tissue  Protects, secretes, absorbs o Simple squamous epithelium o Simple cuboidial epithelium o Simple columnar epithelium o Ciliated epithelium o Pseudostratified ciliated columnar epithelium o Stratified o Stratified Squamous o Stratified Cuboidal o Stratified Columnar o Transitional

Functions of Epithelial Tissue covers the whole surface of the body made up of cells closely packed arranged into one or more layers forms the covering or lining of all internal and external body surfaces packed tightly together separated from the underlying tissue by a thin sheet of connective tissue

Types of Epithelial Tissue Simple Epithelium: only one cell layer thick Stratified Epithelium: two or more cells thick (such as the skin)

Simple Squamous Epithelium have the appearance of thin, flat plates have horizontally flattened, elliptical nuclei because of the thin flattened form of the cell form the lining of cavities such as the blood vessels, heart and lungs and make up the outer layers of the skin Simple Squamous Epithelium

Simple Cubodial Epithelium roughly square or cuboidal in shape. Each cell has a spherical nucleus in the center found in glands and in the lining of the kidney tubules constitute the germinal epithelium which produces egg and sperm Simple Cubodial Epithelium

Simple Columnar Epithelium elongated and column-shaped nuclei are elongated and usually located near base of cells form the lining of the stomach and intestines. Some are specialized for sensory reception (nose, ears and the taste buds) Some secrete mucous to keep surfaces smooth (intestines)

Pseudostratified Ciliated Columnar Epithelium Cilia Single row of cells-appear at different heights secretes & propels (fallopian tubes, nose, bronchi) Found in trachea, etc Goblet Cells- secrete mucus Basal Cells

Stratified Epithelium Found where body linings have to withstand wear and tear top cells are flat and scaly may or may not be keratinized (i.e. containing a tough, resistant protein called keratin). mammalian skin: dry, keratinized, stratified epithelium. lining of the mouth cavity: unkeratinized, stratified epithelium. Basement Membrane

Stratified Squamous Protects underlying cells Skin, throat, mouth

Stratified Cuboidal Protection Lines ducts of mammary glands, sweat glands, pancreas

Stratified Columnar Protection, secretion Male urethra, vas deferens, pharynx

Transitional Specialized to become distended (stretched) Line urinary tract

Connective Tissue

4 Basic Tissue Types Connective Tissue  Supports, binds together, protects o Bone o Adipose Tissue o Areolar Tissue o “White” Fibrous Tissue (Tendon) o “Yellow” Elastic Connective Tissue o Cartilage Hyaline, Elastic, Fibrocartilage o Blood Erythrocytes, Leucocytes, Thrombocytes

Compact Bone Haversian Canal Osteocytes in lacunae Canaliculi Provides internal support of the body_ provides sites of attachment of tendons and muscles, essential for locomotion provides protection for the vital organs of the body: the skull protects the brain; the ribs protect the heart and the main store of calcium and phosphate is in bone.

Adipose Tissue Large, empty-looking cells (adipocytes) with thin margins; nucleus pressed against cell membrane heat insulation, mechanical cushion, a source of energy, space filled as cushioning, body contour Subcutaneous fat beneath the skin & surrounding organs provides insulation provides a buffer for energy imbalances when energy intake is not equal to energy output

Areolar Tissue Holds organs in place and cushions them Attaches epithelial tissue to other underlying tissues. Surrounds blood vessels and nerves

Dense Connective Tissue Composes tissues such as tendons and ligaments Fibrous, can withstand large amounts of stretching and stress Connects muscle to bone fibroblasts

Hyaline Cartilage lacunae Chondrocyte most widespread form of cartilage found in the nasal septum, larynx, trachea and bronchi of the respiratory tract found on the ventral ends of the ribs where they attach to the sternum Composes most of the skeleton of the mammalian fetus has great tensile strength (due to the collagen) highly resistant to pressure

Elastic Cartilage Chondrocyte Lacunae Web-like mesh of elastic fibers Provides structure and strenght External ear and epiglottis

Fibrocartilage lacunae chondrocyte Cartilage containing parallel collagen fibers Provide support, absorb shock, and create padding in some joints Found in meniscus of knee, intervertebral discs of the vertebrae

Blood Leucocytes Erythrocytes Thrombocytes Erythrocytes (Red blood Cells)- contain hemoglobin which allows for transportation of oxygen, anucleated, disc-shaped cells Leukocytes (White Blood Cells) – large, nucleated cells, help to fight infection, 5 different types – each type distinguished by shape of the nucleus Thrombocytes (Platelets)- fragments of a cell, functions in blood clotting

4 Basic Tissue Types Muscle Tissue  Movement  Moving body parts, such as the muscles of arms, legs  Moving substances throughout the body, such as the muscles that make up the blood vessels o Striated (Skeletal) Muscle o Visceral (Smooth) Muscle o Cardiac Muscle

Striated (Skeletal) Muscle striations Unbranched, multi-nucleated fibers bound together in bundles Voluntary muscle, allows for movement Found: along the bones

Visceral (Smooth) Muscle Spindle-shaped fibers(cells) Unbranched, unstriated, uninucleated fibers(cells) Found: internal (visceral) organs- such as esophagus, intestines, stomach, glands, etc.

Cardiac Muscle Intercalated disc Branched, involuntary, striated, multinucleated fibers Has intercalated discs Found: Heart

4 Basic Tissue Types Nerve Tissue  Coordination, communication, integration o Neuron  Dendrites- transport impulses toward the cell body  Axons – transport impulses away from the cell body  Cell body – interprets, coordinates

Nerve Tissue Cell Body Axon Dendrites Made up of neurons (nerve cells) Located in brain, spinal cords, nerves

Transmitting Information The dendrites of neurons receive information from sensory receptors or other neurons. This information is then passed down to the cell body and on to the axon. Once the information has arrived at the axon, it travels down the length of the axon in the form of an electrical signal known as an action potential. Once an electrical impulse has reached the end of an axon, the information is then transmitted to the dendrite of an adjoining neuron.