The Organization of the Human Body (PDF)

The organization of the human body 1. The cell: the unit of life 2. Levels of organization 3. Internan environment and homeostasis  1. The cell: the unit of life The cell is the basic unit of all the living beings. Besides, it is the minimum unit capable of performing th...

The organization of the human body 1. The cell: the unit of life 2. Levels of organization 3. Internan environment and homeostasis  1. The cell: the unit of life The cell is the basic unit of all the living beings. Besides, it is the minimum unit capable of performing the three life functions (nutrition, interaction and reproduction) Cell theory – Robert Hooke (17th century) made the first observations → box-like structures in slices of cork (cells). – Schleiden, Schwann, Virchow y Cajal → formulated the cell theory thanks to their new discoveries. Morphological unit, functional unit, reproductive unit, genetic unit Prokariotic cells (Monera kingdom -bacteria and archaea-) Size between 0,1 and 5 micras No nucleus and the genetic material is dispersed in the citoplasm (nucleoid) They have ribosomes They have cell wall surrounded the cell membrane. Eukaryotic cells Size between 10 and 100 micras. Some cells may be several cm long. They have nucleus. There are animal or plant cells  Cells components: cell membrane It surrounds the cytoplasm and interacts with its environment. It regulates the exchange of substances (semipermeable) Glycocalyx Fluid Mosaic Model Carbohydrates Integral protein Peripherial protein Phospholipid Cholesterol Citoplasm  Gelationous fluid that occupies the inside part of the cell.  It is made up of water and proteins, some of which belong to the cytoskeleton → Network of filaments involved in movement, internal organization and cell division  Cell organelles They organize GOLGI BODY OR APPARATUS CENTRIOLES the cytoskeleton, they are It is involved in responsible of the secretion of the cell motion substances out of and they the cell. participate in cell division. They form the centrosome ENDOPLASMIC RETICULUM (ER) MITOCHONDRIA SMOOTH (ER) Crista Lipid synthesis and detoxification RIBOSOMES It produce most of the ROUGH (ER) energy of a cell through Many ribosomes cellular respiration. are attached to it.It is involved in They are involved in protein synthesis protein synthesis VESICLES Small, rounded organelles that store, transport or digest cellular substances. The lysosomes are digestive vesicles CILIA AND FLAGELLA They are projections involved in cell movement. NUCLEUS  It contains the DNA that forms the genes  It has different parts:  Nuclear envelope with nuclear pores  Nucleoplasm (the fluid found in the nucleus)  Nucleolus (RNA + proteins). Here ribosomes are assembled  Chromatin (DNA + proteins). It condenses into chromosomes. Cell differentiation - Our cells differetiate to specialise in a certain function and act together to make the organism work properly. - Specialised cells perform a certain task, develop chacaracteristic morphology and undergo changes in their cytoplasm depending on the function they perform. 2. Levels of organization Which levels are missing? Muscle cell Muscle tissue Organ (Heart) Organ system (Circulatory System)  Human tissues (Histology) EPITHELIAL TISSUE CONNECTIVE TISSUE MUSCLE TISSUE NERVOUS TISSUE Epithelial tissue There are different types according to the number of layers of cells: Simple epithelia Stratified epithelia Pseudostratified epithelia  Epithelial tissue Their cells are closely packed together without intercellular substance. They are two types: – Glandular epithelia. It makes up the glands that produces and secretes substances. Exocrine glands: They secrete substances outside the body (eg.: sweat glands, liver) Endocrine glands: They secrete hormones into the bloodstream (eg.:thyroid gland) Mixed glands (eg.: pancreas) – Covering epithelia: This tissue covers internal and external body surfaces. It protects these surfaces and it regulates the exchange of substances Epidermis, endothelia, mucous membrane.  Connective tissue It connects other tissues. Componets: cells, fibres and an intercellular substance (matrix) There are several types – Osseous or bone tissue. – Adipose tissue. It protects some organs and store lipids. – Cartilage tissue. It forms the cartilage. – Dense connective tissue. It holds tissues and organs (eg.: tendons, ligaments) – ¿Blood tissue? It transports substances Connective tissue (I). (Dense connective and adipose tissues) Dense conective tissue Fibroblast Collagen fibre Adipose tissue Nucleous of the Fat stored adipocyte Dense connective tissue Connective tissue (II). (Bone and cartilage tissue) Cartilage tissue Chondrocytes Matrix Bone tissue Osteocytes Compact bone Spongy bone tissue tissue  Muscle tissue Skeletal muscle tissue Cardiac muscle tissue Myocyte or muscle fibre It is striated and forms the skeletal muscle to It is also striated. Contraction allow the movement. Contraction is voluntary is involuntary. Smooth muscle tissue They have proteins called actin and Contraction is involuntary. It myosin fibre which is found in the walls of contract and relax internal organs. muscles.  Nervous tissue  There are two types of cells: neurons and glial cells  It transmits and receives information throughout the body.  Organs and organ systems EXAMPLES OF TISSUES Mucle tissue Cartilage tissue Nervous tissue Epithelial tissue EXAMPLES OF ORGANS AND ORGAN SYSTEMS Brain Heart Stomach Bone Nervous Circulatory Digestive Skeleton system Systm system 3. Internal environment and homeostasis  The internal environment is the extracellular fluid where the nutrients and the oxygen necessary for cellular functioning are found, and it is also where cells expel carbon dioxide and waste substances.  It must keep conditions constant to avoid altering cell functioning → homeostasis is the ability to keep the composition and the conditions of the internal environment.  Some homeostatic mechanisms are:  Sweating when we have an excess of heat  Shivering when we feel cold  Urinating to eliminate toxic substances