Baranesmic tissue is responsible for the ventilation process:
Because there are gaps between its constituent cells.
The presence of accompanying cells in the bark tissue:
To supply the sieve pipes with the energy needed to carry out its function.
-----------------------------
Tissues, organs and organ systems:
Most important points:
- Human beings - and other complex multicellular organisms - have organ systems that work together to carry out the processes that keep us alive.
- The body has levels of organization that are built on each other. Cells constitute tissues, tissues constitute organs and organs constitute organ systems.
- The function of an organ system depends on the integrated activity of its organs. For example, the organs of the digestive system cooperate to process food.
- The survival of the organism depends on the integrated activity of all organ systems, often coordinated by the endocrine and nervous systems.
Introduction:
If you were a single-celled organism and lived in a nutrient-rich place, staying alive would be fairly straightforward. For example, if you were an amoeba living in a pond, you could absorb nutrients directly from your environment. The oxygen you would need for your metabolism could diffuse through your cell membrane and carbon dioxide and other debris could diffuse outward. When the time came to reproduce, you could simply divide yourself into two!
However, it is likely that you are not an amoeba - since you are using Khan Academy at this time - and things are not as simple for large multicellular organisms as humans. Your complex body has more than 30 billion cells and most of these cells are not in direct contact with the external environment.
start superscript, end superscript A cell in the depths of your body - in one of your bones, for example, or in your liver - cannot get the nutrients and oxygen it needs directly from the environment.
How is it then that the body feeds its cells and keeps itself functioning? Let's take a closer look at how the organization of your amazing body makes this possible.
Multicellular organisms need specialized systems:
Most cells of large multicellular organisms do not exchange substances directly with the external environment, on the contrary, they are surrounded by an internal environment of extracellular fluid — literally, fluid outside the cells. The cells obtain oxygen and nutrients from the extracellular fluid and release waste products in it. Humans and other complex organisms have specialized systems that take care of the internal environment, and keep it constant and able to meet the needs of cells.
Different systems of the body perform different functions. For example, your digestive system is responsible for taking and processing food, while your respiratory system - which works with the circulatory system - is responsible for taking oxygen and eliminating carbon dioxide. The muscular and skeletal systems are crucial for movement, the reproductive system is responsible for reproduction and the excretory system eliminates metabolic wastes.
Due to their specialization, different systems depend on each other. Each of the cells that make up the digestive, muscular, skeletal, reproductive and excretory systems need oxygen from the respiratory system to function and the cells of the respiratory system - like all other systems - need nutrients and must get rid of metabolic wastes. All body systems work together to keep the organism functioning.
Summary of the organization of the body:
All living organisms are made up of one or more cells. Unicellular organisms, such as amoebas, are made up of only one cell. Multicellular organisms, such as people, are made up of many cells. Cells are considered the fundamental unit of life.
Cells in complex multicellular organisms such as people are organized into tissues, similar groups of cells that work together on a specific task. Organs are structures composed of two or more tissues that are organized to perform a particular function; Organ groups with related functions make up the different organ systems.
At each level of organization - cells, tissues, organs and organ systems - the structure is closely related to the function. For example, small intestine cells that absorb nutrients look very different from the muscle cells necessary for body movement. The structure of the heart reflects its function of pumping blood throughout the body, while the structure of the lungs maximizes the efficiency with which they can take oxygen and release carbon dioxide.
Types of fabrics:
As we saw earlier, each organ is composed of two or more tissues, groups of similar cells that work together to perform a specific task. Humans - and other large multicellular animals - are made up of four basic types of tissue: epithelial tissue, connective tissue, muscle tissue and nerve tissue.
Epithelial tissue:
The epithelial tissue is made up of tight sheets of cells that line the surfaces, including the outside of the body, and line the body's cavities. For example, the outer layer of the skin is an epithelial tissue, as is the lining of the small intestine.
Epithelial cells are polarized, which means they have an upper and a lower side. The apical, upper side of an epithelial cell faces the inside of a cavity or the outside of a structure and is generally exposed to liquid or air. The basal, inferior side faces the underlying cells. For example, the apical side of intestinal cells have finger-shaped structures that increase the surface with which they absorb nutrients.
The epithelial cells are very attached and this allows them to act as a barrier to the movement of liquids and potentially harmful microbes. The cells are usually joined by cell junctions that keep them in close proximity to reduce leaks.
Connective tissue:
Connective tissue consists of cells suspended in an extracellular matrix. In most cases, the matrix is composed of protein fibers such as collagen and fibrin in a solid, liquid or gelatinous base substance. The connective tissue supports and, as the name implies, connects other tissues.
Loose connective tissue, shown below, is the most common type of connective tissue. It is found throughout your body and supports organs and blood vessels, in addition to joining the epithelial tissues of the underlying muscles. Dense or fibrous connective tissue is found in tendons and ligaments, which connect muscles with bones and bones with other bones, respectively.
Some specialized forms of connective tissue include adipose tissue - body fat - bone, cartilage and blood, which has a liquid extracellular matrix called plasma.
Muscle tissue:
Muscle tissue is essential to keep the body erect and moving, and even to pump blood and move food through the digestive tract.
Muscle cells, often called muscle fibers, contain actin and myosin proteins, which allow them to contract. There are three main types of muscle: skeletal muscle, heart muscle and smooth muscle.
Skeletal muscle, also called striated (striped) muscle, is what we refer to as muscle in everyday life. The skeletal muscle is attached to the bones by tendons and allows you to consciously control your movements. For example, the quadriceps of your legs or the biceps of your arms are skeletal muscle.
The heart muscle is only found in the walls of the heart. Like the skeletal muscle, the heart muscle is striated, or scratched. But it's not under voluntary control, so - luckily! - you don't need to think about making your heart keep beating. The individual fibers are connected by structures called intercalated discs, which allow them to contract in synchrony.
Smooth muscle is found in the walls of blood vessels, as well as in the walls of the digestive tract, the uterus, the urinary bladder and other internal structures. The smooth muscle is not scratched or striated, and is involuntary, it is not under conscious control. That means you don't have to think about moving food through the digestive tract!
Nervous tissue:
The nervous tissue participates in the detection of stimuli - external or internal signals - and the processing and transmission of information. This tissue consists mainly of two types of cells: neurons, or nerve cells, and glia.
Neurons are the basic functional unit of the nervous system. They generate electrical signals called nerve impulses or action potentials that allow neurons to transmit information very quickly over long distances. The main function of the glia is to support neuronal function.
