cell and tissues

• The smallest living unit of all living things is called CELL
• Cell structure


  • Cell membrane
  • Nucleus
  • Cytoplasm
• Cell membrane


  • It separates the cell from the external environment
  • It gives shape to the cell
  • It plays a role in the exchange of substances
  • It consists of protein, fat, a small amount of carbohydrates
  • Double layer (consists of protein molecules embedded between two layers of fat)
  • Carbohydrates combine with fats in the cell membrane to form glycolipids which combine with proteins to form glycoproteins (Golgi synthesizes glycolipid and glycoprotein)
  • There are pores on it that allow the exchange of substances
  • It is selectively permeable
• Cytoplasm


  The liquid part made up of organelles
• Organelles in cytoplasm


  • Endoplasmic reticulum
  • Ribosome
  • Mitochondria
  • Lysosome
  • Golgi
• Endoplasmic reticulum (ER)


  • Channels extending between the cell membrane and the nucleus
  • It provides the transport and storage of substances within the cell
  • It makes the nuclear membrane and the golgi
  • By dividing the cell into compartments, it allows acidic and basic reactions in the cytoplasm to be carried out without affecting each other
  • If there is a ribosome on it, it is granular, if there is no ribosome, it is granular
  • Granular ER is abundant in enzyme-secreting cells, and non-granular ER is abundant in fat-synthesizing cells
• Ribosome


  • It is produced in the nucleolus
  • They are either attached to the endoplasmic reticulum membrane or found free
  • It consists of protein and rRNA
  • Makes protein and enzyme synthesis
• Golgi


  • More present in secreting cells
  • It produces secretions (liquids) such as sweat, milk, tears and saliva, wrapping them with a membrane and packaging them
  • Packs enzymes to form lysosome
  • Participates in cell membrane construction (glycoprotein, glycolipid synthesis)
• Lysosome


  • It is in the form of a sac consisting of a single layered membrane
  • It carries strong digestive enzymes (hydrolase, lipase, phosphatase)
  • If the lysosome membrane structure is damaged, the cell digests itself (autolysis)
  • It is more abundant in cells specialized for phagocytosis such as macrophages and leukocytes
  • Digestion of nutrients taken from the outside into the cell
  • Digesting and neutralizing bacteria and toxins that enter the cell from the outside
  • Digestion of organelles and structures that have lost their function in the cell
  • Enzymes in it are produced in ribosomes
  • The enzymes produced are transported by the ER
  • Enzymes transported by the ER are packaged in the golgi
  • The Golgi surrounds these enzymes with a membrane, forming the lysosome
  • Ribosome, golgi and ER are effective in the formation of lysosome
• Secondary lysosomes


  • Also known as heterophagosomes or digestive vacuoles
  • These lysosomes form when primary lysosomes, which contain inactive hydrolytic enzymes, fuse with endosomes
  • The endosomes can include phagosomes (containing food particles or pathogens) or pinosomes (containing extracellular materials)
  • In secondary lysosomes, the previously inactive digestive enzymes become active, allowing for the digestion of various substances
  • After digestion, these lysosomes release their contents into the cytoplasm through a process called exocytosis
• Mitochondria


  • It has double membranes
  • The inner membrane is folded. The folds are called cristae, and the liquid filling between and inside the membranes is called matrix
  • It produces and stores energy by respiration with oxygen
  • The number of cells that need more energy, such as muscles, nerves and liver, is higher
  • They gather in the parts of the cell where they are most in need of energy
• Centrosome


  • It consists of two subunits called centrioles
  • During cell division, it replicates itself and is pulled to opposite poles and provides the formation of spindle fibers
  • It provides chromosome movement during division
  • It forms structures such as cilia extending out of the cell
• Nucleus


  • It contains genetic material
  • It controls cell division. In this way, the genetic material is transferred to new cells
  • It controls protein synthesis
• Nucleus Membrane


  • It has a double-layered membrane
  • It prevents hereditary material from being disintegrated by dispersing into the cytoplasm
  • Macromolecules can pass through the pores on it
• Nucleus Matrix


  Same as cytoplasmic fluid, less fluidity
• Chromatin


  When the cell divides, they shorten and thicken to form chromosomes
• Nucleolus


  • It contains DNA, RNA and proteins
  • Ribosome synthesis is done
• Tissue


  It consists of cells that have the same structure and come together to do the same job, and the intercellular substance (matrix) surrounding them
• Types of Tissue


  • Epithelial Tissue
  • Connective Tissue
  • Muscle Tissue
  • Nervous Tissue
• Epithelial Tissue


  • It surrounds the entire outer and inner surface of the body
  • It has functions such as suction, secretion, transport, excretion, protection, contraction (myoepithelial cells) and sensory reception (specialized hair cells in the retina and ear)
  • Flat / Cubic / Prismatic (=cylindrical, =columnar)
  • Single layer / Multi-layer / Pseudostratified
• Single layer squamous epithelium

  • Found on diffusion and filtration surfaces
  • Endothelium - blood vessels and lymphatic vessels
  • Mesothelium - alveoli (Lung)
• Stratified squamous epithelium


  • Keratinized / Non-keratinized (Epidermis, oral cavity, esophagus, pharynx, vagina, cornea)
• Single-layered cuboidal epithelium


  • Secretory and absorptive functions are performed (Thyroid follicles, kidney tubules, pancreatic acini)
• Stratified cubic epithelium


  • Excretory ducts of sweat and salivary glands, ducts of mammary glands
• Single-layer columnar epithelium


  • They are responsible for secretion and absorption. They are found from the stomach to the end of the digestive tract
• Stratified columnar epithelium


  • Very rare in the body (Prostate, some large excretory channels, a section of the urethra)
• Pseudostratified columnar epithelium


  • Very common throughout the body. Usually ciliated (Respiratory tracts (Trachea, Large bronchi))
• Transitional Epithelium


  • These cells can change shape between squamous and cubic epithelium according to the functioning of the organ. It lays the urinary system.
• Connective Tissue


  • Provides and maintains the shape of the body
  • Connects cells and organs to each other
  • Fibroblasts, Fibrils (Collagen, Elastic, Reticular)
• Cartilage tissue


  • Chondrocytes, matrix (acid mucopolysaccharide)
• Bone tissue


  • Osteocyte, Osteoblast, Osteoclast and Calcified intermediate matrix
• Muscle Tissue


  • Smooth muscle (involuntary movements)(digestive system organs, blood vessels)
  • Striated muscle (voluntary movements)
  • heart muscle
• Tissues by proliferation capacity


  • Continuously dividing cells (Cells that are constantly losing and proliferating. Example: Hematopoietic cells, skin, oral cavity, vagina, cervical surface epithelium etc)
  • Stable cells (Cells with a low mitotic rate but proliferate by dividing in case of injury or tissue loss. Example: Liver, Kidney, Pancreas)
  • Static cells (Cells that no longer divide (neurons and skeletal muscle cells) or rarely divide (smooth-heart muscle). They divide only in the embryonic period)
• Cell Division


  The formation of new cells from a cell
• Purpose of cell division

  • To breed
  • To ensure the growth and development of tissues, organs and systems, repair of worn-out tissues, and replacement of dead cells
  • The division order is given by the DNA molecule in the nucleus
• Types of cell division

  • Binary fission (in prokaryotes)
  • Mitosis (in eukaryotes)
  • Meiosis (in eukaryotes)
• Cell division in eukaryotes

  • Mitosis - vegetative division, producing daughter cells genetically identical to the parent cell
  • Meiosis - cell division that produces haploid gametes for sexual reproduction, reducing the number of chromosomes from two of each type in the diploid parent cell to one of each type in the daughter cells
• Difference between meiosis and mitosis

  • Mitosis involves the division of body cells, while meiosis involves the division of sex cells or gametes
  • Mitosis produces two identical, diploid daughter cells, while meiosis produces four non-identical, haploid daughter cells
  • Mitosis involves a single round of cell division, while meiosis involves two rounds of cell division
  • Mitosis maintains the same number and kind of chromosomes as the parent cell, while meiosis reduces the number of chromosomes by half and creates genetic variation
• Stages of Cell Cycle

  • Mitosis
  • Interphase (G1, S, G2)
• G1 (Pre-duplication) stage


  • The genetic character of the cells emerging from the previous mitosis is the same as the mother, but the volume is half the mother's. In order for these cells to reach the mother cell volume, a rapid RNA + protein synthesis occurs
  • Most of the cells leave the cycle at the end of the G1 phase (G0 cells). When a suitable stimulus (such as injury) comes, they resume mitosis from where they left off