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Organization of the human body 13/11/11 Organization of the human body 2 © Zanichelli editore 2016 2 2

Organization of the body in animals 13/11/11 Organization of the body in animals Animals present some characteristics that distinguish them from unicellular organisms and provide specific advantages: cells are specialized; there is hierarchical organization; cells are organized into tissues which compose organs that work together in systems; cells communicate and cooperate. 3 © Zanichelli editore 2016 3 3

The human body The human body has four types of tissues: 13/11/11 The human body The human body has four types of tissues: epithelial tissue; connective tissue; muscle tissue; nervous tissue. These tissues form organs which are organized into eleven systems. 4 © Zanichelli editore 2016 4 4

13/11/11 Epithelial tissues Epithelial tissues are formed by one or more layers of cells of regular shape that don’t contain blood vessels. They cover the surfaces of organs and blood vessels. The epithelium rests on a basement membrane and its cells are continuously replaced. epithelium 5 © Zanichelli editore 2016 5 5

Functions of epithelial tissues 13/11/11 Functions of epithelial tissues Epithelial tissues have different functions: protection and covering; controlled exchange of substances; secretion (endocrine and exocrine glands); sensory reception (receptors). 6 © Zanichelli editore 2016 6 6

13/11/11 Connective tissues Connective tissues fill and connect different parts of the body. They are formed by cells dispersed in a solid, semi-solid or fluid matrix. They are divided into connective tissues – proper and special connective tissues. Proper connective tissues include: loose connective tissue; dense connective tissue; fat tissue. 7 © Zanichelli editore 2016 7 7

Special connective tissues 13/11/11 Special connective tissues Type of tissue Functions Matrix bone tissue protection, support, storage of calcium and phosphorus solid matrix cartilage protection of joints in response to friction and tension resistant, strong and flexible matrix blood supply oxygen and nutrients to tissues, waste removal, immunological function, regulation of body temperature fluid matrix (plasma) 8 © Zanichelli editore 2016 8 8

13/11/11 Muscle tissues Muscle tissues are formed by elongated cells, called fibers, that can contract and relax, facilitating movement. There are different types of muscle tissues: skeletal or striated muscle which contracts voluntarily; smooth muscle which contracts involuntarily; cardiac muscle (in the heart) which contracts involuntarily. 9 © Zanichelli editore 2016 9 9

Nervous tissue Nervous tissue is formed by neurons and glial cells. 13/11/11 Nervous tissue dendrites Nervous tissue is formed by neurons and glial cells. Neurons are cells that present: a cell body, containing the nucleus; dendrites, specialized in the reception of stimuli ; an axon, that transports nervous signals from the cell to other neurons or organs. cell body axon 10 © Zanichelli editore 2016 10 10

13/11/11 Integumentary system The integumentary system covers and protects the body. It consists of skin and accessory organs (glands, nails, hair, sensory receptors and free nerve endings). epidermis The skin is formed by two main layers: epidermis; dermis. Below the dermis is the hypodermis – a layer of fat tissue. dermis hypodermis 11 © Zanichelli editore 2016 11 11

13/11/11 Skeletal system The skeletal system supports and protects the internal organs, supports muscles, produces (in the red bone marrow) blood cells, and is involved in calcium equilibrium. axial skeleton The skeleton is divided into the: axial skeleton (skull, rib cage, vertebral column); appendicular skeleton (upper and lower limbs, shoulder girdle, pelvic girdle). appendicular skeleton 12 © Zanichelli editore 2016 12 12

13/11/11 Skeleton and muscles The skeleton provides rigid support for mucles, with which it forms an integrated system. Bones act as levers, producing ordered movements with help from coordinated action of different muscles. 13 © Zanichelli editore 2016 13 13

13/11/11 Homeostasis Homeostasis is the body’s ability to maintain a stable inner environment even when external conditions change. To maintain homeostasis, cells communicate via signal molecules. There are two mechanisms used to maintain homeostasis: positive feedback; negative feedback. 14 © Zanichelli editore 2016 14 14

13/11/11 Thermoregulation Body temperature control (thermoregulation) is an important part of homeostasis. Humans are endothermic, with a body temperature around 37 °C. Thermoregulation occurs by controlling the production of internal heat and the exchange of heat between the body and the environment (perspiration, vasoconstriction, vasodilation, muscle activities). The control center of body temperature is the hypothalamus. 15 © Zanichelli editore 2016 15 15

Stem cells and cell differentiation 13/11/11 Stem cells and cell differentiation Stem cells are undifferentiated cells that can proliferate, generating copies of themselves or specialized cells. Stem cells can be divided into: totipotent cells; pluripotent cells; multipotent cells; unipotent cells. totipotent pluripotent multipotent unipotent 16 © Zanichelli editore 2016 16 16

Regulation of cell growth and death 13/11/11 Regulation of cell growth and death The growth and regeneration of cells is regulated by several signal molecules. When cells proliferate without control, it is possible to develop hyperplasia or tumors. Cell death can occur through two mechanisms: apoptosis - a controlled death; necrosis - caused by trauma. 17 © Zanichelli editore 2016 17 17