The Animal Body and Principles of Regulation Chapter 43

2 Organization of Vertebrate Body There are four levels of organization: 1.Cells 2.Tissues 3.Organs 4.Organ systems

3 Organization of Vertebrate Body Tissues are groups of cells that are similar in structure and function The three fundamental embryonic tissues are called germ layers –Endoderm, mesoderm and ectoderm In adult vertebrates, there are four primary tissues –Epithelial, connective, muscle and nerve

4 Organization of Vertebrate Body Organs are combinations of different tissues that form a structural and functional unit Organ systems are groups of organs that cooperate to perform the major activities of the body –The vertebrate body contains 11 principal organ systems

5 Organization of Vertebrate Body examples

6 Organization of Vertebrate Body The body plan of all vertebrates is essentially a tube within a tube –Inner tube - Digestive tract –Outer tube - Main vertebrate body Supported by a skeleton –Outermost layer - Skin and its accessories Inside the body are two identifiable cavities

7 Organization of Vertebrate Body 1.Dorsal body cavity - Within skull and vertebrae 2.Ventral body cavity - Bounded by the rib cage and vertebral column and divided by the diaphragm into: –Thoracic cavity - heart and lungs Pericardial cavity: around the heart Pleural cavity: around the lungs –Abdominopelvic cavity - most organs Peritoneal cavity - coelomic space around organs

8 Organization of Vertebrate Body

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10 Organization of Vertebrate Body

11 Organization of Vertebrate Body

12 1. Epithelial Tissue An epithelial membrane, or epithelium, covers every surface of the vertebrate body –Can come from any of the 3 germ layers –Some epithelia change into glands Cells of epithelia are tightly bound together –Provide a protective barrier Epithelia possess remarkable regenerative powers replacing cells throughout life

13 1. Epithelial Tissue Epithelial tissues attach to underlying connective tissues by a fibrous membrane –Basal surface - Secured side –Apical surface - Free side Therefore, epithelia have inherent polarity, which is important for their function

14 1. Epithelial Tissue Two general classes –Simple - one layer thick –Stratified - several layers thick Subdivided by shape into: –Squamous cells - flat –Cuboidal cells - cube-shaped –Columnar cells - cylinder-shaped

15 Simple Epithelium Simple squamous epithelium –Lines lungs and blood capillaries Simple cuboidal epithelium –Lines kidney tubules and several glands Simple columnar epithelium –Lines airways of respiratory tract and most of the gastrointestinal tract –Contains goblet cells that secrete mucus

16 Simple Epithelium Glands of vertebrates form from invaginated epithelia Exocrine glands –connected to epithelium by a duct –e.g. sweat, sebaceous and salivary glands Endocrine glands –ductless –secretions (=hormones) enter blood

17 Stratified Epithelium Named according to the features of their apical (free side) cell layers –Epidermis is a stratified squamous epithelium Characterized as a keratinizedepithelium Contains water-resistant keratin Note: Lips are covered with nonkeratinized, stratified squamous epithelium

18 2. Connective Tissues Derive from embryonic mesoderm Divided into two major classes –Connective tissue proper –Loose or dense –Special connective tissue Cartilage, bone and blood All have abundant extracellular material called the matrix –Protein fibers plus ground substance Ground substance is fluid material containing an array of proteins and polysaccharides

19 Connective Tissue Proper Fibroblasts produce and secrete extracellular matrix Loose connective tissue –Cells scattered within a matrix that contains large amounts of ground substance –Strengthened by protein fibers such as: Collagen – Supports tissue Elastin – Makes tissue elastic

20 Connective Tissue Proper Adipose cells (fat cells) also occur in loose connective tissue –Develop in large groups in certain areas, forming adipose tissue

21 Connective Tissue Proper Dense connective tissue –Contains less ground substance and more collagen than loose connective tissue Dense regular connective tissue –Collagen fibers line up in parallel –Makes up tendons and ligaments Dense irregular connective tissue: –Collagen fibers have different orientations –Covers kidney, muscles, nerves & bone

22 Special Connective Tissue Cartilage –Ground substance made from characteristic glycoprotein, called chondroitin, and collagen fibers in long, parallel arrays –Flexible with great tensile strength –Found in joint surfaces and other locations –Chondrocytes (cartilage cells) live within lacunae (spaces) in the ground substance

23 Special Connective Tissue Bone –Osteocytes (bone cells) remain alive in a matrix hardened with calcium phosphate Blood –Extracellular material is the fluid plasma –Erythrocytes - red blood cells –Leukocytes - white blood cells –Thrombocytes - platelets

24 3. Muscle Tissue Muscles are the motors of vertebrate bodies –Three kinds: smooth, skeletal and cardiac –Skeletal and cardiac muscles are also known as striated muscles –Skeletal muscle is under voluntary control, whereas contraction of smooth and cardiac is involuntary

25 3. Muscle Tissue Smooth muscles are found in walls of blood vessels and visceral organs –Cells are mono-nucleated Skeletal muscles are usually attached to bone by tendons, so muscle contraction causes bones to move –Muscle fibers (cells) are multi-nucleated Contract by means of myofibrils, that contain ordered actin and myosin filaments

26 3. Muscle Tissue Cardiac muscle is composed of smaller, interconnected cells –Each cell has a single nucleus –Interconnections appear as dark lines called intercalated disks –Enable cardiac muscle cells to form a single functioning unit

27 4. Nerve Tissue Cells include neurons and their supporting cells called neuroglia Most neurons consist of three parts –Cell body: contains the nucleus –Dendrites: highly branched extensions conduct electrical impulses toward the cell body –Axon: single cytoplasmic extension Conducts impulses away from cell body

28 4. Nerve Tissue Neuroglia do not conduct electrical impulses –Support and insulate neurons and eliminate foreign materials in and around neurons Associate with axon to form an insulating cover called the myelin sheath –Gaps, known as nodes of Ranvier, are involved in acceleration of impulses

29 4. Nerve Tissue Nervous system is divided into: –Central nervous system (CNS) Brain and spinal cord Integration and interpretation of input –Peripheral nervous system (PNS) Nerves and ganglia (collections of cell bodies) Communication of signal to body

30 Overview of Organ Systems Communication and integration –Three organ systems detect external stimuli and coordinate the body’s responses –Nervous, sensory and endocrine systems

31 Overview of Organ Systems Support and movement –The musculoskeletal system consists of the interrelated skeletal and muscular organ systems

32 Overview of Organ Systems Regulation and maintenance –Four organ systems regulate and maintain the body’s chemistry Digestive, circulatory, respiratory and urinary systems

33 Overview of Organ Systems Defense –The body defends itself with two organ systems: integumentary and immune

34 Overview of Organ Systems Reproduction and development –The biological continuity of vertebrates is the province of the reproductive system –In females, the system also nurtures the developing embryo and fetus

35 Homeostasis As animals have evolved, specialization of body structures has increased For cells to function efficiently and interact properly, internal body conditions must be relatively constant The dynamic constancy of the internal environment is called homeostasis It is essential for life

36 Homeostasis

37 Homeostasis To maintain internal constancy, the vertebrate body uses negative feedback mechanisms –Changing conditions are detected by sensors (cells or membrane receptors) –Information is fed to an integrating center, also called comparator (brain, spinal cord or endocrine gland) –Compares conditions to a set point

38 Homeostasis If a deviation is detected, a message is sent to an effector (muscle or gland) –Increase or decrease in activity brings internal conditions back to set point –Negative feedback to the sensor terminates the response

39 Homeostasis

40 Homeostasis Humans have set points for body temperature, blood glucose concentrations, electrolyte (ion) concentration, tendon tension, etc. We are endothermic: can maintain a relatively constant body temperature (37 o C or 98.6 o F) –Changes in body temperature are detected by the hypothalamus in the brain

41 Homeostasis Negative feedback mechanisms often oppose each other to produce finer degree of control –Many internal factors are controlled by antagonistic effectors Have “push-pull” action Increasing activity of one effector is accompanied by decrease in the other

42 Homeostasis Antagonistic effectors are involved in the control of body temperature –If hypothalamus detects high temperature Promotes heat dissipation via sweating, and dilation of blood vessels in skin –If hypothalamus detects low temperature Promotes heat conservation via shivering and constriction of blood vessels in skin

43 Homeostasis room body

44 Homeostasis In a few cases, the body uses positive feedback mechanisms to enhance a change –These do not in themselves maintain homeostasis –However, they are generally part of some larger mechanism that does! –Examples: Blood clotting Contraction of uterus during childbirth

45 Homeostasis