Lecture 17 Transport in Animals

Tissues: Most animal cells are organized into tissues. Cooperative unit of very similar cells that perform a specific function. Tissue comes from Latin word meaning “weave”. Cells of tissues may be held together by: Fibers Glue-like substance Plasma membrane structures. Tissue structure is related to its function.

Tissues There are four main types of animal tissue: 1. Epithelial 2. Connective 3. Muscle 4. Nervous

Epithelial Tissue Cells are tightly fitted together in continuous layers or sheets. Cover outside of body (skin), line organs and internal body cavities (Mucous membranes of digestive, respiratory, and reproductive systems). Tight packaging allows tissue to act as a barrier to protect against mechanical injury, infection, and fluid loss. Two surfaces: Free surface: Exposed to air or fluid. Bottom surface: Attached to underlying tissues by a basement membrane, a dense layer of protein and polysaccharides.

Epithelial Tissue Can be classified based on two criteria: A. Number of layers: Simple: One layer. Stratified: Several layers B. Shape of cells: Squamous: Flat cells. Cuboidal: Cube shaped cells Columnar: Column shaped cells Example: Simple squamous epithelium Stratified columnar epithelium

Epithelial Tissue Covers and Lines the Body and its Parts A. Simple squamous (Lung air sacs) D. Statified squamous (Lining esophagus) B. Simple cuboidal (Kidney tubes) C. Statified columnar (Lining intestine)

Epithelial Tissue Some epithelial tissues, such as mucous membranes, absorb and secrete chemical solutions. Mucous membranes: Digestive tract epithelium (mucous membranes) secretes mucus and digestive enzymes. Respiratory tract epithelium secretes mucous that helps trap dust particles before they reach the lungs.

Connective Tissue Relatively few cells surrounded by large amounts of nonliving material (matrix). Cells secrete the matrix, which can be solid, liquid, or gelatinous. Diverse functions. Mainly bind, support, and connect other tissues.

Connective Tissue Binds and Provides Support A. Loose Connective Tissue D. Fibrous Connective Tissue B. Adipose Tissue E. Cartilage C. Blood F. Bone

Six Types of Connective Tissue in Humans 1. Loose Connective Tissue: Most widespread connective tissue in vertebrates. Loose matrix with fibers, packing material. Attaches skin to muscles, binds and holds tissues and organs in place. 2. Adipose (fat): Pads and insulates body. Energy storage. 3. Blood: Fluid matrix (plasma) has water, salts, and proteins. Red and white blood cells. 4. Fibrous Connective Tissue: Matrix of densely packed collagen fibers. Strong and nonelastic. Found in: Tendons: Attach muscles to bones. Ligaments: Attach bone to bone. 5. Cartilage: Rubbery matrix with collagen fibers. Found on end of bones, nose, ears, and between vertebra. 6. Bone: Supports the body of most vertebrates. Solid matrix of collagen fibers and calcium, phosphate, and magnesium salts. Bone is harder than cartilage, but not brittle because of collagen.

Muscle Tissue Most abundant type of tissue in most animals. Accounts for two-thirds (2/3) of human weight. Specialized for contraction. Made up of long cells that contract when stimulated by nerve impulses. Muscle cells have many microfilaments made up of actin and myosin. Muscle contraction accounts for much of energy consuming work in animals. Adults have a fixed number of muscle cells. Weight lifting doesn’t increase number of muscle cells, only their size.

Muscle Tissue There are three types of muscle tissue: A. Skeletal (striated) muscle : Attached to bones by tendons. Responsible for voluntary movements. B. Cardiac muscle: Forms contractile tissue of heart. Not under voluntary control. C. Smooth muscle: Found in walls of digestive tract, bladder, arteries, uterus, and many internal organs. Responsible for peristalsis and labor contractions. Contract more slowly than skeletal muscle, but can remain contracted longer. Not under voluntary control.

Three Types of Muscle B. Cardiac muscle A. Skeletal muscle C. Smooth muscle

Nervous Tissue Senses stimuli and transmits signals from one part of the animal to another. Controls the activity of muscles and glands, and allows the animal to respond to its environment. Neuron: Nerve cell. Structural and functional unit of nervous tissue. Consists of: Cell body : Contains cell’s nucleus. Dendrite: Extension that conveys signals towards the cell body. Axon: Extension that transmits signals away from the cell body. Supporting cells: Nourish, protect, and insulate neurons.

Nervous Tissue Forms a Communication Network

Organs Are Made up of Different Tissues Organ: Several tissues that act as a unit and together perform one or more biological functions. Perform functions that component tissues can’t carry out alone. Example: The heart is an organ made up of: Muscle Tissue: Contraction. Epithelial Tissue: Lines heart chambers to prevent leakage and provide a smooth surface. Connective Tissue: Makes heart elastic and strengthens its walls and valves. Nervous Tissue: Direct heart contraction.

Organs are Made of Several Different Tissues

Transport Systems Diffusion/passive transport and active transport ways to exchange material. In larger complex organism cells separated by each other and external environment. Need to transport nutrients, gases, and wastes to and from cells. Need a system which can move substances rapidly.

Transport Systems in Animals Alimentary – food and water moved Respiratory – air and water moved Blood vascular – blood Lymphatic - lymph

Components of A Circulatory System Blood: a connective tissue of liquid plasma and cells. Heart: a muscular pump to move the blood. Blood vessels: arteries, capillaries and veins that deliver blood to all tissues. 3 types – open system, closed system and lymphatic system. Functions: Exchange gases with the respiratory system. Supplies tissues with oxygen. Removes carbon dioxide from tissues. Transports materials (nutrients, hormones, etc.) inside body. Defends against infection.

1. Open Circulatory Systems Common to molluscs and arthropods. Pump blood into a hemocoel with the blood diffusing back to the circulatory system between cells. Blood is pumped by a heart into the body cavities, where tissues are surrounded by the blood. The resulting blood flow is sluggish.

2. Closed Circulatory Systems Have the blood closed at all times within vessels of different size and wall thickness. In this type of system, blood is pumped by a heart through vessels, and does not normally fill body cavities. Blood flow is not sluggish. Hemoglobin causes vertebrate blood to turn red in the presence of oxygen; but more importantly hemoglobin molecules in blood cells transport oxygen. The human closed circulatory system is sometimes called the cardiovascular system.

3. Lymphatic System Returns fluid and proteins that have leaked from blood capillaries into tissues. Up to 4 liters of fluid every day. Fluid returned near heart/venae cavae.

Blood 1. Plasma 2. Red Blood Cells 3. White Blood Cells 4. Platelets Has 4 components:- 1. Plasma 2. Red Blood Cells 3. White Blood Cells 4. Platelets

1. Plasma Liquid component of the blood. 60% of blood is plasma. Plasma is made up of 90% water and 10% dissolved materials including proteins, glucose, ions, hormones, and gases. It acts as a buffer, maintaining pH near 7.4. Plasma contains nutrients, wastes, salts, proteins. Serum is plasma that no longer contains fibrinogen, a protein involed in clotting.

2. Red Blood Cells Also known as erythrocytes, Flattened, doubly concave cells about 7 µm in diameter. Carry oxygen associated in the cell's hemoglobin. Mature erythrocytes lack a nucleus. They are small, 4 to 6 million cells per cubic millimeter of blood, and have 200 million hemoglobin molecules per cell. Humans have a total of 25 trillion (about 1/3 of all the cells in the body). Red blood cells are continuously manufactured in red marrow of long bones, ribs, skull, and vertebrae. Life-span of an erythrocyte is only 120 days, after which they are destroyed in liver and spleen. Iron from hemoglobin is recovered and reused by red marrow. The liver degrades the heme units and secretes them as pigment in the bile, responsible for the color of feces. Each second 2 million red blood cells are produced to replace those taken out of circulation.

3. White Blood Cells Also known as leukocytes, Larger than erythrocytes, have a nucleus, and lack hemoglobin. They function in the cellular immune response. White blood cells (leukocytes) are less than 1% of the blood's volume. They are made from stem cells in bone marrow. There are five types of leukocytes, important components of the immune system. Neutrophils enter the tissue fluid by squeezing through capillary walls and phagocytozing foreign substances. Macrophages release white blood cell growth factors, causing a population increase for white blood cells. Lymphocytes fight infection. T-cells attack cells containing viruses. B-cells produce antibodies. Antigen-antibody complexes are phagocytized by a macrophage. White blood cells can squeeze through pores in the capillaries and fight infectious diseases in interstitial areas.

4. Platelets Platelets are cell fragments that bud off megakaryocytes in bone marrow. Involved with clotting. They carry chemicals essential to blood clotting. Platelets survive for 10 days before being removed by the liver and spleen. There are 150,000 to 300,000 platelets in each milliliter of blood. Platelets stick and adhere to tears in blood vessels; they also release clotting factors. A hemophiliac's blood cannot clot. Providing correct proteins (clotting factors) has been a common method of treating hemophiliacs. It has also led to HIV transmission due to the use of transfusions and use of contaminated blood products.

Electron Micrograph of Blood

Blood Clotting Thromboplastin – lipoprotein released from injured tissue. Clotting factors – enzymes in plasma. Calcium ions. Prothrombin catalysed to thrombin (protease). Thrombin hydrolyses fibrinogen (large soluble protein) to fibrin (insoluble). Blood cells become trapped in the fibrin mesh and a clot forms. Dries and forms a barrier to prevent further blood loss. Does not occur in undamaged blood vessels. Heparin is an anticoagulant. If clot forms in blood circulation it is called a thrombus, leads to thrombosis.