HUMAN ANATOMY

 

HUMAN ANATOMY:  the discipline of human anatomy deals with the organization of the human body and the way body organs are arranged in relation to each other.  It is only when we know very well this type of organisation that we can be able to allocate abnormalities and their possible causes when it comes to disease states.  In our discussion here, we are going to be looking at some of the most visible and immediate human body organs and the way they are related to each other.  You may also want to read about the following disciplines; Human physiology, 

LEUKOCYTES

 

Characteristics of Leukocytes: Although leukocytes and erythrocytes both originate from hematopoietic stem cells in the bone marrow, they are very different from each other in many significant ways. For instance, leukocytes are far less numerous than erythrocytes: Typically there are only 5000 to 10,000 per µL. Bloodand its components  

They are also larger than erythrocytes and are the only formed elements that are complete cells, possessing a nucleus and organelles.  And although there is just one type of erythrocyte, there are many types of leukocytes. Most of these types have a much shorter lifespan than that of erythrocytes, some as short as a few hours or even a few minutes in the case of acute infection.  One of the most distinctive characteristics of leukocytes is their movement. Whereas erythrocytes spend their days circulating within the blood vessels, leukocytes routinely leave the bloodstream to perform their defensive functions in the body’s tissues. For leukocytes, the vascular network is simply a highway they travel and soon exit to reach their true destination. When they arrive, they are often given distinct names, such as macrophage or microglia, depending on their function. They leave the capillaries, the smallest blood vessels or other small vessels through a process known as emigration or diapedesis in which they squeeze through adjacent cells in a blood vessel wall.  Once they have exited the capillaries, some leukocytes will take up fixed positions in lymphatic tissue, bone marrow, the spleen, the thymus, or other organs. Others will move about through the tissue spaces very much like amoebas, continuously extending their plasma membranes, sometimes wandering freely, and sometimes moving toward the direction in which they are drawn by chemical signals. The plasma membrane  

This attracting of leukocytes occurs because of positive chemotaxis, a phenomenon in which injured or infected cells and nearby leukocytes emit the equivalent of a chemical “911” call, attracting more leukocytes to the site. In clinical medicine, the differential counts of the types and percentages of leukocytes present are often key indicators in making a diagnosis and selecting a treatment.

RELATED;

1.  HUMAN LEUKOCYTE ANTIGEN

2.  THE HUMAN RED BLOOD CELLS

3.  ANATOMY AND PHYSIOLOGY

REFERENCES

BODY ORGANS

BODY ORGANS:  The huma body is organized into macromolecules, cellular  organelles, cells, Body organs, tissues and then systems in the ascending order of complexity.  At the organ level, we have more specialization and complexity of different tissues that function together the normal body processes to run, and the human body has 100s of them.  On this page, we are going to look some of the most immediate and paramount body organs without which the human body will be in struggle, and then we shall also see the most common diseases that affect them.

THE HUMAN BRAIN:  The human brain is one of the most vital organs in the human body, for it controls all the processes running either asleep or arousable.  The brain is part of the central nervous system and it contains 1000s of centers controlling millions of processes that runs the body from birth to death.  The human brain weighs about 1.5 to 1.7 Kg for an average individual and is found in the most upper part of the skull.  Some of the most common illnesses that affect the brain include but not limited to;  Meningitis, Cerebral vascular accident also known as stroke, and Altered level of consciousness as detailed in the embedded links.

THE HEART:  The human heart is another very vital organ in the body.  It acts as the pump that delivers blood throughout the body tissues delivering between 5-7 litres of blood in about 72 seconds of an adult human being.  The heart starts pumping early in life when the human embryo is still around 4 weeks of gestation, during which period many organs are forming int the fetus and we call this period between 3-8 weeks the period of organogenesis.  It continues to pump throughout life and it is one organ that we can assess to determine the level of well being.  Some of the conditions that affect the human heart include but not limited to the following; Hypertension, Heart failure, Angina and Myocardia infarction.

LUNGS:  The lungs are some of the most vital organs of the human body because of their role in gaseous exchange.

RELATED;

1.  BODY TISSUES

2.  THE HUMAN KIDNEYS

3.  THE LIVER

4.  THE BLOOD-BRAIN BARRIER

5.  CHAMBERS AND CIRCULATION THROUGH THE HEART

6. CYTOPLASM AND CELLULAR ORGANELLES

7.  MENINGITIS

8.  STROKE

9.  ALTERED LEVEL OF CONSCIOUSNESS

10.  HYPETENSION

11.  HEART FAILURE

BLOOD-BRAIN BARRIER

 

INTRODUCTION:  The blood–brain barrier (BBB) is a highly selective permeability barrier that separates the circulating blood from the brain extracellular fluid in the central nervous system (CNS).  The blood–brain barrier is formed by brain endothelial cells, which are connected by tight junctions with an extremely high electrical resistivity.

SELECTIVITY OF THE MEMBRANE:  The blood–brain barrier allows the passage of water, some gases, and lipid soluble molecules by passive diffusion, as well as the selective transport of molecules such as glucose and amino acids that are crucial to neural function.  On the other hand, the blood–brain barrier may prevent the entry of lipophilic, potential neurotoxins by way of an active transport mechanism mediated by P-glycoprotein.

CELLULAR ACTECTURE OF THE BBB:  Astrocytes are necessary to create the blood–brain barrier. A small number of regions in the brain, including the circumventricular organs (CVOs), do not have a blood–brain barrier.  The blood–brain barrier occurs along all capillaries and consists of tight junctions around the capillaries that do not exist in normal circulation.  Endothelial cells restrict the diffusion of microscopic objects such as bacteria and large or hydrophilic molecules into the cerebrospinal fluid (CSF), while allowing the diffusion of small or hydrophobic molecules including O₂, CO₂, hormones).  Cells of the barrier actively transport metabolic products such as glucose across the barrier with specific proteins. This barrier also includes a thick basement membrane and astrocytic end feet.

RELATED;

1.  IMPULSE PROPAGATION IN THE CNS

2.  METABOLIC PROFILE OF THE BRAIN

3.  ANATOMY AND PHYSIOLOGY

REFERENCES

THE ENTERIC NERVOUS SYSTEM

 

INTRODUCTION:  The enteric nervous system is composed of interconnected networks of ganglion cells and nerve fibers mainly located in the submucosa (submucosal plexus) and between the circular and longitudinal muscle layers (myenteric plexus). These networks give rise to nerve fibers that connect with the mucosa and muscle.  Although extrinsic sympathetic and parasympathetic nerves project onto the submucosal and myenteric plexuses, the enteric nervous system can independently regulate gastrointestinal motility and secretion.  Extrinsic primary afferent neurons project via the dorsal root ganglia or vagus nerve to the central nervous system.  Release of serotonin (5-HT) from intestinal mucosa enterochromaffin (EC) cells stimulates 5-HT 3 receptors on the extrinsic afferent nerves, stimulating nausea, vomiting, or abdominal pain.  Serotonin also stimulates submucosal 5-HT 1P  receptors of the intrinsic primary afferent nerves (IPANs), which contain calcitonin gene-related peptide (CGRP) and acetylcholine and project to myenteric plexus interneurons. 5-HT 4  receptors on the presynaptic terminals of the IPANs appear to enhance release of CGRP or acetylcholine. The myenteric interneurons are important in controlling the peristaltic reflex, promoting release of excitatory mediators proximally and inhibitory mediators distally. Motilin may stimulate excitatory neurons or muscle cells directly. Dopamine acts as an inhibitory neurotransmitter in the gastrointestinal tract, decreasing the intensity of esophageal and gastric contractions.

RELATED;

1.  INITIATION OF A NERVE IMPULSE

2.  SYNAPSES  

REFERENCES