46.0 Introduction

1. Vertebrates Are Representative Animals
1. All Vertebrates Share the Same Body Plan and Operation fig 46.1
2. Humans Are Representative Vertebrates of Special Importance

46.1 The bodies of vertebrates are organized into functional systems

1. Organization of the Body
1. General Body Architecture fig 46.2
1. Digestive tube suspended within internal body cavity
2. Diaphragm divides coelom into two parts
1. Thoracic cavity: Heart and lungs
2. Abdominal cavity: Stomach, intestines and liver

3. Supported by internal skeleton of jointed bones
1. Bony skull surrounds brain
2. Column of hollow vertebrae surrounds dorsal spinal nerve cord

4. Four levels of organization in the body
1. Cells tissues organs organ systems
2. Bodies composed of many different types of cells

2. Tissues
1. Groups of cells with similar structure and functions are called tissues
2. Three fundamental embryonic tissues: Endoderm, mesoderm and ectoderm
3. Four principal adult primary tissues: Epithelial, connective, muscle, nerve fig 46.3

3. Organs and Organ Systems
1. Organs are a structural and functional unit composed of different tissues fig 46.4
1. Example: The heart
2. Contains cardiac muscle, connective tissue, epithelial tissue
3. Laced with nerves to regulate heart beat

2. Organ system is group of organs that function together to carry out body activities
1. Digestive system composed of digestive tract, liver, gall bladder, pancreas
2. Humans contain eleven principal organ systems tbl 43.1 fig 46.5

46.2 Epithelial tissue forms membranes and glands

1. Characteristics of Epithelial Tissue
1. Epithelium Covers Every Surface of the Body
1. Examples
1. Epidermis derived from ectoderm, comprises outer layer of skin
2. Inner surface of digestive tract lined with endoderm derived epithelium
3. Inner surface of body cavities lined with mesoderm derived epithelium

2. Functions of epithelial tissues
1. Provide selectively barrier
1. Any entering or exiting substance must cross an epithelial layer
2. Facilitate or impede passage of materials into underlying tissues

2. Protect underlying tissue from dehydration and mechanical damage
3. Secrete materials via glands

3. Characteristics of epithelial layers
1. Cells bound tightly together
2. Are only a few cell layers thick
3. Possess few blood vessels, transport materials via diffusion
4. Readily regenerated

4. Two general classes tbl 46.2
1. Simple epithelium
2. Stratified epithelium
3. Further subdivided by cell shape
1. Simple squamous: Flat cells
2. Simple cuboidal: Equal height and width
3. Columnar: Height greater than width

2. Types of Epithelial Tissues
1. Simple epithelial membrane fig 46.3
1. A single cell layer thick
2. Simple squamous cells
1. Have irregular, flattened shape with tapered edges
2. Line lungs and blood capillaries
3. Permit rapid passage of molecules across membrane

3. Simple cuboidal cells line small ducts inside glands
4. Simple columnar cells line respiratory and gastrointestinal tract
1. Interspersed with goblet cells
2. Respiratory tract cells have cilia
3. Surface of intestine has microvilli projections to increase surface area

2. Stratified epithelial membrane
1. Several cell layers thick, named according to features of uppermost layers
2. Epidermis is a stratified squamous epithelium
1. Has an upper layer of squamous cells
2. Terrestrial vertebrates have keratinized epithelium
1. Superficial cells are dead and filled with keratin
2. Keratin increased in response to abrasion forming calluses
3. Lips covered by nonkeratinized, stratified squamous epithelium

3. Glands
1. Derived from invaginated epithelia,produce various substances
2. Two categories of glands
1. Exocrine glands: Connected to epithelium by a duct
1. Product channeled to outside or to body cavity
2. Sweat and oil glands channel products externally
3. Accessory digestive glands are internal

2. Endocrine glands: Connection with epithelium lost, ductless
1. Secretions called hormones
2. Hormones enter blood capillaries, don't leave body

46.3 Connective tissues perform a variety of functions

1. Connective Tissue Proper
1. Structural Building Blocks fig 46.3
1. Derived from mesoderm
2. Divided into two categories
1. Connective tissue proper: Loose and dense
2. Special connective tissue: Cartilage, bone, blood

3. Composed of widely-spaced cells imbedded in an extracellular matrix

2. Loose Connective Tissue
1. Strengthened by collagen, elastin and/or reticulin fig 46.6
2. Fibroblasts secrete collagen and fibrous proteins
3. Contains other living cells
1. Mast cells produce histamine and heparin
2. Phagocytic macrophages defend against invading organisms

4. May contain adipose cells fig 46.7
1. Each cell stores a droplet of fat (triglycerides)
2. Number of fat cells in an adult is usually fixed, can change in size

3. Dense Connective Tissue
1. Contains tightly packed collagen fibers
2. May be regular or irregular
1. In dense regular tissue collagen fibers are lined up in parallel
1. Tendons bind muscle to bone
2. Ligaments bind bone to bone

2. In dense irregular tissue, fibers have different orientations
1. Tough coverings of organs like capsules of kidneys and adrenal glands
2. Perimysium covers muscles, perineurium covers nerves, periosteum covers bones

2. Specialized Connective Tissue
1. Cartilage fig 46.8
1. Has special ground substance made from characteristic glycoprotein
2. Collagen fibers laid down along lines of stress
3. Produces firm, flexible tissue that is tough and doesn't stretch
4. Makes up skeleton of agnathans, cartilaginous fishes, cushions bone joints
5. Chondrocytes remain alive even with no blood vessels
1. Receive oxygen and nutrients by diffusion from surrounding blood vessels
2. Diffusion occurs because cartilage matrix is not calcified like bone

2. Bone fig 46.9
1. Many bones in fetus first modeled in cartilage
2. Cartilage hardened by calcification, cells die, replaced by living bone
3. Osteocytes are living bone cells, matrix is hardened with calcium phosphate
4. Blood vessels travel through canals in bone
1. Osteocytes communicate with blood vessels through canals
2. Canals called canaliculi

3. Blood fig 46.10
1. Contains abundant matrix material: Fluid plasma
2. Cells include erythrocytes (red cells) and leukocytes (white cells)
3. Thrombocytes or platelets are fragments of a type of bone marrow cell
4. Erythrocytes are the most common blood cells
1. Lose nucleus, mitochondria and ER during maturation
2. Metabolically are relatively inactive
3. Has iron-containing hemoglobin protein, carries oxygen

5. Several types of leukocytes
1. Have nuclei and mitochondria, no hemoglobin
2. Neutrophils, eosinophils, basophils have special affinity to biological stains
3. Lymphocytes and monocytes are other components of immune system

6. Blood plasma contains nutrients, metabolic wastes, regulatory molecules
1. Also contains sodium, calcium, other inorganic salts
2. Includes proteins like fibrinogen and albumin
3. Contains lymphocyte-produced antibodies

46.4 Muscle tissue provides for movement and nerve tissue provides for regulation

1. Muscle Tissue
1. Muscle Cells Are Motors of the Vertebrate Body
1. Possess large numbers of actin and myosin filaments, specialized for contraction
2. Three types of vertebrate muscle: Smooth, skeletal and cardiac fig 46.4
3. Skeletal and cardiac are also striated muscles

2. Smooth Muscle
1. Earliest form to evolve, found throughout animal kingdom
2. Cells are long and spindle-shaped, each with one nucleus
3. Cells organized into sheets to form smooth muscle tissue
4. Two types of contraction occur
1. All muscles contract as a unit when stimulated by nerve
1. Muscles lining blood vessels
2. Muscles of iris

2. Individual cells contract spontaneously
1. Causes slow, steady contraction of the tissue
2. Muscles in the walls of the gut
3. Nerves regulate activity, do not cause it

3. Skeletal Muscle
1. Attached to bones by tendons, contract and cause bones to move
2. Numerous parallel muscle cells called muscle fibers, act in concert
3. Stronger contractions result when more fibers stimulated to contract by nerve
1. Nerves vary strength of muscle contraction
2. Contraction due to substructures called myofibrils fig 46.11
3. Contain highly ordered arrays of actin and myosin filaments

4. Fibers produced during development by the fusion of several cells
1. A single fiber runs the length of an individual vertebrate muscle
2. Each fiber contains all of the original nuclei of the fused cells

4. Cardiac Muscle
1. Vertebrate hearts made of specially arranged striated muscle fibers
1. Composed of interconnected cells, each with its own nucleus
2. Interconnections appear as lines called intercalated disks fig 46.10
3. Lines are really regions where cells are linked by gap junctions

2. Interconnections allow heart to contract as single unit
1. Functioning unit called myocardium
2. Certain muscle cells generate spontaneous electrical impulse
3. Impulses spread across gap junction from cell to cell
4. All cells in myocardium ultimately contract

2. Nerve Tissue
1. Composition of Nerve Tissue
1. Neurons: Specialized for transmission of nerve impulses
2. Composed of three parts: Cell body, dendrites, axon fig 46.12
3. Cell body contains the nucleus
4. Dendrites
1. Thin, highly branched protrusions from the cell body
2. Receive stimulation
3. Conduct electrical events to cell body

5. Axon
1. Transmit nerve impulse away from the cell body
2. Long tubular extension of the cell body
3. Axon can be long, resulting in long nerve cell
4. May be covered with insulating layer called myelin sheath
5. Periodic interruptions in sheath called nodes of Ranvier

2. Nerves Are Bundles of Axon Fibers
1. Central nervous system (CNS): Include brain and spinal cord
2. Peripheral nervous system (PNS): Include nerves and ganglia