The liver is the second largest organ in the body - only the skin is bigger and heavier. The functions of the human liver are related to digestion, metabolism, immunity, and the storage of nutrients in the body. The liver is a vital organ, without which the tissues of the body quickly die from a lack of energy and nutrients. Luckily, she has an incredible ability to regenerate and is able to grow very fast to regain her function and size. Let's look at the structure and functions of the liver in more detail.
Macroscopic human anatomy
The human liver is located on the right under the diaphragm and has a triangular shape. Most of its mass is located on the right side, and only a small part of it extends beyond the midline of the body. The liver consists of very soft, pinkish-brown tissues encased in a connective tissue capsule (Glison's capsule). It is covered and reinforced by the peritoneum (serosa) of the abdomen, which protects and holds it in place within the abdomen. The average size of the liver is approximately 18 cm in length and no more than 13 in thickness.
The peritoneum connects to the liver atfour locations: coronary ligament, left and right triangular ligaments, and teres ligament. These connections are not unique in the anatomical sense; rather, they are compressed areas of the abdominal membrane that support the liver.
• The broad coronary ligament connects the central part of the liver to the diaphragm.
• Located at the lateral borders of the left and right lobes, the left and right triangular ligaments connect the organ to the diaphragm.
• The curved ligament runs down from the diaphragm through the anterior edge of the liver to its bottom. At the bottom of the organ, a curved ligament forms a round ligament and connects the liver to the navel. The round ligament is a remnant of the umbilical vein that carries blood to the body during embryonic development.
The liver consists of two separate lobes - left and right. They are separated from each other by a curved ligament. The right lobe is about 6 times larger than the left. Each lobe is divided into sectors, which, in turn, are divided into segments of the liver. Thus, the body is divided into two parts, 5 sectors and 8 segments. The segments of the liver are numbered in Latin numerals.
Right share
As mentioned above, the right lobe of the liver is approximately 6 times larger than the left. It consists of two large sectors: the lateral right sector and the paramedian right sector.
The right lateral sector is divided into two lateral segments that do not border the left lobe of the liver: the lateral superior posterior segment of the right lobe (VII segment) and the lateral inferior posterior segment (VI segment).
The right paramedian sector also consists of twosegments: middle upper anterior and middle lower anterior segments of the liver (VIII and V, respectively).
Left share
Despite the fact that the left lobe of the liver is smaller than the right one, it consists of more segments. It is divided into three sectors: left dorsal, left lateral, left paramedian sector.
The left dorsal sector consists of one segment: the caudate segment of the left lobe (I).
The left lateral sector is also formed from one segment: the posterior segment of the left lobe (II).
The left paramedian sector is divided into two segments: the quadrate and anterior segments of the left lobe (IV and III, respectively).
You can consider in more detail the segmental structure of the liver in the diagrams below. For example, figure one shows the liver, which is visually divided into all its parts. The segments of the liver are numbered in the figure. Each number corresponds to the Latin segment number.
Pattern 1:
Bile capillaries
The tubes that carry bile through the liver and gallbladder are called bile capillaries and form a branched structure - the bile duct system.
Bile produced by liver cells drains into microscopic channels - bile capillaries, which combine to form large bile ducts. These bile ducts then join together to form large left and right branches that carry bile from the left and right lobes of the liver. Later they unite into one common hepatic duct, into which allbile.
The common hepatic duct finally joins the cystic duct from the gallbladder. Together they form the common bile duct, carrying bile to the duodenum of the small intestine. Most of the bile produced by the liver is put back into the cystic duct by peristalsis and remains in the gallbladder until it is needed for digestion.
Circulatory system
The blood supply to the liver is unique. Blood enters it from two sources: the portal vein (venous blood) and the hepatic artery (arterial blood).
The portal vein carries blood from the spleen, stomach, pancreas, gallbladder, small intestine, and greater omentum. Upon entering the gates of the liver, the venous vein divides into a huge number of vessels, where the blood is processed before moving to other parts of the body. Leaving the liver cells, the blood is collected in the hepatic veins, from which it enters the vena cava and returns to the heart.
The liver also has its own system of arteries and small arteries that provide oxygen to its tissues just like any other organ.
Wedges
The internal structure of the liver is made up of approximately 100,000 small hexagonal functional units known as lobules. Each lobule consists of a central vein surrounded by 6 hepatic portal veins and 6 hepatic arteries. These blood vessels are connected by many capillary-like tubes called sinusoids. Like spokes on a wheel, they extend from the portal veins and arteries towards the centralVienna.
Each sinusoid passes through liver tissue, which contains two major cell types: Kupffer cells and hepatocytes.
• Kupffer cells are a type of macrophage. In simple terms, they trap and break old, worn-out red blood cells passing through sinusoids.
• Hepatocytes (liver cells) are cuboidal epithelial cells found between the sinusoids and make up the majority of cells in the liver. Hepatocytes perform most of the functions of the liver - metabolism, storage, digestion, and bile production. Tiny collections of bile, known as bile capillaries, run parallel to the sinusoids on the other side of the hepatocytes.
Scheme of the liver
We are already familiar with the theory. Let's now see what the human liver looks like. You will find photos and descriptions for them below. Since one drawing cannot show the whole organ, we use several. It's okay if two images show the same part of the liver.
Picture 2:
The number 2 marks the human liver itself. Photos in this case would not be appropriate, so consider it according to the drawing. Below are the numbers, and what is shown under this number:
1 - right hepatic duct; 2 - liver; 3 - left hepatic duct; 4 - common hepatic duct; 5 - common bile duct; 6 - pancreas; 7 - pancreatic duct; 8 - duodenum; 9 - sphincter of Oddi; 10 - cystic duct; 11 - gallbladder.
Pattern 3:
If you've ever seen an atlas of human anatomy, you know that it contains approximately the same images. Here the liver is shown from the front:
1 - inferior vena cava; 2 - curved ligament; 3 - right share; 4 - left lobe; 5 - round ligament; 6 - gallbladder.
Pattern 4:
In this picture, the liver is shown from the other side. Again, the human anatomy atlas contains almost the same figure:
1 - gallbladder; 2 - right share; 3 - left lobe; 4 - cystic duct; 5 - hepatic duct; 6 - hepatic artery; 7 - hepatic portal vein; 8 - common bile duct; 9 - inferior vena cava.
Pattern 5:
This picture shows a very small part of the liver. Some explanations: the number 7 in the figure shows the triad portal - this is a group that unites the hepatic portal vein, hepatic artery and bile duct.
1 - hepatic sinusoid; 2 - liver cells; 3 - central vein; 4 - to the hepatic vein; 5 - bile capillaries; 6 - from intestinal capillaries; 7 - "triad portal"; 8 - hepatic portal vein; 9 - hepatic artery; 10 - bile duct.
Picture 6:
Inscriptions in English are translated as (from left to right): right lateral sector, right paramedian sector, left paramedian sector and left lateral sector. Segments of the liver are numbered in white numbers, each number corresponds to the Latin number of the segment:
1 - right hepatic vein; 2 - left hepatic vein; 3 - middle hepatic vein; 4 - umbilical vein (residue); 5 - hepatic duct; 6 - inferior vena cava; 7 - hepatic artery; 8 - portal vein; 9 - bile duct; 10 - cystic duct; 11 - gallbladder.
Liver physiology
The functions of the human liver are very diverse: it plays a serious role in digestion, metabolism, and even in the storage of nutrients.
Digestion
The liver plays an active role in the process of digestion through the production of bile. Bile is a mixture of water, bile s alts, cholesterol and the pigment bilirubin.
After the hepatocytes in the liver produce bile, it travels through the bile ducts and is stored in the gallbladder until needed. When a meal containing fat reaches the duodenum, duodenal cells release the hormone cholecystokinin, which relaxes the gallbladder. Bile, moving through the bile ducts, enters the duodenum, where it emulsifies large masses of fat. Emulsification of fats with bile converts large lumps of fat into small pieces that have less surface area and are therefore easier to process.
Bilirubin, which exists in bile, is a product of the liver processing worn-out red blood cells. Kupffer cells in the liver trap and destroy old, worn-out red blood cells and transfer them to hepatocytes. In the latter, the fate of hemoglobin is decided - it is divided into heme and globin groups. The globin protein is further broken down and used as a sourceenergy for the body. The iron-containing heme group cannot be processed by the body and is simply converted to bilirubin, which is added to bile. It is bilirubin that gives bile its distinctive greenish color. Intestinal bacteria further convert bilirubin to the brown pigment strecobilin, which gives feces a brown color.
Metabolism
The hepatocytes of the liver are entrusted with quite a lot of complex tasks associated with metabolic processes. Because all blood leaves the digestive system through the hepatic portal vein, the liver is responsible for converting carbohydrate, lipids and proteins into biologically useful materials.
Our digestive system breaks down carbohydrates into the monosaccharide glucose, which cells use as their main source of energy. The blood entering the liver through the hepatic portal vein is extremely rich in glucose from digested food. Hepatocytes take up most of this glucose and store it as glycogen macromolecules, a branched polysaccharide that allows the liver to store large amounts of glucose and release it quickly between meals. Glucose uptake and release by hepatocytes help maintain homeostasis and lower blood glucose levels.
Fatty acids (lipids) from the blood passing through the liver are taken up and metabolized by hepatocytes to produce energy in the form of ATP. Glycerol, one of the lipid components, is converted by hepatocytes into glucose through the process of gluconeogenesis. Hepatocytes can also produce lipids such as cholesterol, phospholipids and lipoproteins,which are used by other cells throughout the body. Most of the cholesterol produced by hepatocytes is excreted from the body as a component of bile.
Dietary proteins are broken down into amino acids by the digestive system before they are delivered to the hepatic portal vein. The amino acids entering the liver require metabolic processing before they can be used as an energy source. Hepatocytes first remove the amine group from the amino acids and convert it to ammonia, which is eventually converted to urea.
Urea is less toxic than ammonia and can be excreted in the urine as a waste product of digestion. The remaining parts of the amino acids are broken down into ATP or converted into new glucose molecules through the process of gluconeogenesis.
Detoxification
As blood from the digestive organs travels through the portal circulation of the liver, hepatocytes control the blood content and remove many potentially toxic substances before they can reach the rest of the body.
Enzymes in hepatocytes convert many of these toxins (like alcohol or drugs) into their inactive metabolites. In order to keep hormone levels within homeostatic limits, the liver also metabolizes and removes hormones produced by its own glands from the circulation.
Storage
The liver provides storage for many essential nutrients, vitamins and minerals obtained from the transfer of blood through the hepatic portal system. GlucoseIt is transported in hepatocytes under the influence of the hormone insulin and stored as glycogen polysaccharide. Hepatocytes also absorb fatty acids from digested triglycerides. The storage of these substances allows the liver to maintain blood glucose homeostasis.
Our liver also stores vitamins and minerals (vitamins A, D, E, K and B 12, as well as iron and copper minerals) to ensure a constant supply of these important substances to the tissues of the body.
Production
The liver is responsible for the production of several vital plasma protein components: prothrombin, fibrinogen and albumin. Prothrombin and fibrinogen proteins are coagulation factors involved in the formation of blood clots. Albumins are proteins that maintain an isotonic environment in the blood so that body cells do not gain or lose water in the presence of body fluids.
Immunity
The liver functions as an organ of the immune system through the function of Kupffer cells. Kupffer cells are macrophages that form part of the mononuclear phagocyte system along with macrophages of the spleen and lymph nodes. Kupffer cells play an important role as they recycle bacteria, fungi, parasites, worn-out blood cells and cell breakdown products.
Liver ultrasound: norm and deviations
The liver performs many important functions in our body, so it is very important that it is always normal. Considering the fact that the liver cannot get sick because it has no nerve endings, you may not noticehow the situation became hopeless. It may simply be destroyed, gradually, but in such a way that in the end it will be impossible to cure it.
There are a number of liver diseases in which you will not even feel that something irreparable has happened. A person can live and consider himself he althy for a long time, but in the end it turns out that he has cirrhosis or liver cancer. And that can't be changed.
Although the liver has the ability to recover, it will never cope with such diseases on its own. Sometimes she needs your help.
To avoid unnecessary problems, it is enough just to visit a doctor sometimes and do an ultrasound of the liver, the norm of which is described below. Remember that the most dangerous diseases are associated with the liver, for example, hepatitis, which, without proper treatment, can lead to such serious pathologies as cirrhosis and cancer.
Now let's go directly to the ultrasound and its norms. First of all, the specialist looks to see if the liver is displaced and what are its dimensions.
It is impossible to specify the exact dimensions of the liver, since it is impossible to fully visualize this organ. The length of the entire organ should not exceed 18 cm. Doctors examine each part of the liver separately.
Let's start with the fact that on the ultrasound of the liver, two of its lobes, as well as the sectors into which they are divided, should be clearly visible. In this case, the ligamentous apparatus (that is, all ligaments) should not be visible. The study allows physicians to study all eight segments separately, as they are also clearly visible.
Normal size of the right and left lobe
The left lobe should be approximately 7 cm inthickness and about 10 cm in height. An increase in size indicates he alth problems, perhaps that you have an inflamed liver. The right lobe, the norm of which is about 12 cm in thickness and up to 15 cm in length, as you can see, is much larger than the left one.
In addition to the organ itself, doctors must also look at the bile duct, as well as the large vessels of the liver. The size of the bile duct, for example, should be no more than 8 mm, the portal vein should be about 12 mm, and the vena cava should be up to 15 mm.
For doctors, not only the size of the organs is important, but also their structure, the contours of the organ and their tissue.
The human anatomy (whose liver is a very complex organ) is quite a fascinating thing. There is nothing more interesting than understanding the structure of oneself. Sometimes it can even save you from unwanted diseases. And if you are vigilant, problems can be avoided. Going to the doctor is not as scary as it seems. Stay he althy!
