Which mature cells have a nucleus

A nucleosome is a single, wrapped DNA-histone complex. Multiple nucleosomes along the entire molecule of DNA appear like a beaded necklace, in which the string is the DNA and the beads are the associated histones. It is estimated that humans have almost 22, genes distributed on 46 chromosomes. The nucleus is the command center of the cell, containing the genetic instructions for all of the materials a cell will make and thus all of its functions it can perform.

The nucleus is encased within a membrane of two interconnected lipid bilayers, side-by-side. This nuclear envelope is studded with protein-lined pores that allow materials to be trafficked into and out of the nucleus. The nucleus contains one or more nucleoli, which serve as sites for ribosome synthesis.

The nucleus houses the genetic material of the cell: DNA. DNA is normally found as a loosely contained structure called chromatin within the nucleus, where it is wound up and associated with a variety of histone proteins.

When a cell is about to divide, the chromatin coils tightly and condenses to form chromosomes. The nucleolus specifically functions in the formation of which of the following structures? Place the following structures in order from least to most complex organization: chromatin, nucleosome, DNA, chromosome.

A reduction in the total binding capacity of hemoglobin to oxygen i. Human erythrocytes are produced through a process called erythropoiesis. They take about seven days to mature. Human erythrocytes are produced through a process called erythropoiesis, developing from committed stem cells to mature erythrocytes in about seven days.

When matured, these cells circulate in the blood for about to days, performing their normal function of molecule transport. At the end of their lifespan, they degrade and are removed from circulation. Scanning electron micrograph of blood cells : Shown on the left, the erythrocyte, or red blood cell, has a round, donut-like shape. Erythropoiesis is the process in which new erythrocytes are produced, which takes about seven days. Erythrocytes are continuously produced in the red bone marrow of large bones at a rate of about 2 million cells per second in a healthy adult.

Erythrocytes differentiate from erythrotropietic bone marrow cells, a type of hemopoietic stem cell found in bone marrow. Unlike mature RBCs, bone marrow cells contain a nucleus. In the embryo, the liver is the main site of red blood cell production and bears similar types of stem cells at this stage of development.

Erythropoiesis can be stimulated by the hormone erythropoietin, which is synthesized by the kidney in response to hypoxia systemic oxygen deficiency. These dietary nutrients that are necessary for proper synthesis of hemoglobin iron and normal RBC development B12 and folic acid.

Just before and after leaving the bone marrow, the developing cells are known as reticulocytes. These immature RBCs that have shed their nuclei following initial differentiation.

After 24 hours in the bloodstream, reticulocytes mature into functional RBCs. Eryptosis, a form of apoptosis programmed cell death , is the aging and death of mature RBCs.

As an RBC ages, it undergoes changes in its plasma membrane that make it susceptible to selective recognition by macrophages and subsequent phagocytosis in the reticuloendothelial system spleen, liver, and bone marrow. This process removes old and defective cells and continually purges the blood. Eryptosis normally occurs at the same rate as erythropoiesis, keeping the total circulating red blood cell count in a state of equilibrium.

Many diseases that involve damage to RBCs hemolytic anemias, sepsis, malaria, pernicious or nutritional anemias or normal cellular processes that cause cellular damage oxidative stress may increase the rate of eryptosis. Conversely, erythropotein and nitric oxide a vasodilator will inhibit eryptosis. Following eryptosis, the hemoglobin content within the RBC is broken down and recirculated throughout the body.

The heme components of hemoglobin are broken down into iron ions and a green bile pigment called biliverdin. The biliverdin is reduced to the yellow bile pigment bilirubin, which is released into the plasma and recirculated to the liver, then bound to albumin and stored in the gallbladder.

The bilirubin is excreted through the digestive system in the form of bile, while some of the iron is released into the plasma to be recirculated back into the bone marrow by a carrier protein called transferrin.

This iron is then reused for erythropoiesis, but additional dietary iron is needed to support healthy RBC life cycles. Privacy Policy. Skip to main content. Cardiovascular System: Blood. Search for:. Red Blood Cells. RBC Anatomy Red blood cells lack nuclei and have a biconcave shape.

It also facilitates oxygen transport. Red blood cells are considered cells, but they lack a nucleus, DNA, and organelles like the endoplasmic reticulum or mitochondria. Red blood cells cannot divide or replicate like other bodily cells. They cannot independently synthesize proteins. However, hemoglobin does not carry all the carbon dioxide in the blood back to the lungs—the blood can also transport CO2 as a dissolved gas or as bicarbonate HCO3.

Like red blood cells, platelets are derived from myeloid stem cells. Some of these stem cells develop into megakaryoblasts, which give rise to cells called megakaryocytes in the bone marrow. After a megakaryocyte has matured, pieces of its cytoplasm break away into cell fragments called platelets. A single megakaryocyte can produce — platelets. However, they do contain numerous granules or vesicles. The hormone thrombopoietin, produced by the liver and kidneys, regulates the production of megakaryocytes and platelets.

Platelets have different appearances in their inactivated and activated states. When inactivated , platelets are irregularly shaped discs. Activated platelets are spherical, with protrusions that allow them to stick to wound tissue and to other platelets to form a plug at the site of a blood vessel tear.

Activated platelets also release chemicals from their granules to initiate clotting. The life span of a platelet is about 10 days. Like red blood cells, old platelets are phagocytosed. Reserve platelets are stored in the spleen. When a blood vessel tears, platelets adhere to the damaged blood vessel wall near the tear, forming a platelet plug.

At this point, they change from their inactive to their active shape, and they empty the contents of their granules. At the site of an injury, the platelets connect to one another and release chemicals that stimulate blood clotting.