SPERM CELLS

The term sperm is derived from the Greek word (σπέρμα) sperma (meaning "seed")
and refers to the male reproductive cells. In the types of sexual reproduction known as anisogamy and oogamy, there is a marked difference in the size of the gametes with the smaller one being termed the "male" or
sperm cell. The human sperm cell is haploid, so that its 23 chromosomes can join the 23
chromosomes of the female egg to form a diploid cell. A uniflagellar sperm cell that is motile is referred to as a spermatozoon, whereas a non-motile sperm cell is
referred to as a spermatium. Sperm cells cannot divide and have a limited life span,
but after fusion with egg cells during fertilization, a new organism begins
developing, starting as a totipotent zygote.[citation needed] The spermatozoa of animals are produced through spermatogenesis inside the male gonads (testicles) via meiotic division. They are carried out of the male body in a
fluid known as semen. Mammalian sperm cells can survive within the female
reproductive tract for more than 5 days post coitus.[1] Sperm cells in algal and many plant gametophytes are produced in male gametangia (antheridia) via mitotic division. In flowering plants, sperm nuclei are produced inside pollen.[citation needed] Etymology The term "sperm" probably comes from
sperma which in Greek is "seed" or Latin
"something sown". Other terms for sperm
include "prostatic fluid" and "seminal fluid"
and "seed". Origin Sperm originates solely from the testicles, and this is where sperm develop. The
initial spermatozoon process takes around 70 days to complete. The spermatid stage is where the sperm develops the familiar
tail. The next stage where it becomes fully
mature takes around 60 days when its called a spermatozoan.[2] Subsequently, the semen wherein the sperm is carried is produced in the seminal vesicles, prostate gland and urethral glands. AnatomySperm fertilizing an egg The sperm cell consists of a head, a
midpiece and a tail. The head contains the nucleus with densely coiled chromatin fibres, surrounded anteriorly by an acrosome, which contains enzymes used for penetrating the female egg. The
midpiece has a central filamentous core
with many mitochondria spiralled around
it, used for ATP production for the journey through the female cervix, uterus and uterine tubes. The tail or "flagellum" executes the lashing movements that propel the spermatocyte.[citation needed] During fertilization, the sperm provides three essential parts to the oocyte: (1) a signalling or activating factor, which
causes the metabolically dormant oocyte to activate; (2) the haploid paternal genome; (3) the centrosome, which is responsible for maintaining the microtubule system.[3] Motile sperm cells Motile sperm cells of algae and seedless plants.[4] Motile sperm cells typically move via flagella and require a water medium in order to swim toward the egg for
fertilization. Most of the energy for sperm
motility is derived from the metabolism of fructose carried in the seminal fluid. This takes place in the mitochondria located in the sperm's midpiece (at the base of the
sperm head). These cells cannot swim
backwards due to the nature of their
propulsion. The uniflagellated sperm cells
(with one flagellum) produced in most animals are referred to as spermatozoa, and are known to vary in size.[citation needed] Motile sperm are also produced by many protists and the gametophytes of bryophytes , ferns and some gymnosperms such as cycads and ginkgo. The sperm cells are the only flagellated cells in the life
cycle of these plants. In many ferns and lycophytes , they are multi-flagellated (carrying more than one flagellum).[4] In nematodes, the sperm cells are amoeboid and crawl, rather than swim, towards the egg cell.[5] Non-motile sperm cells Non-motile sperm cells called spermatia lack flagella and therefore cannot swim.
Spermatia are produced in a spermatangium.[4] Because spermatia cannot swim, they
depend on their environment to carry them
to the egg cell. Some red algae, such as Polysiphonia, produce non-motile spermatia that are spread by water currents after their release.[4] The spermatia of rust fungi are covered with a sticky substance. They are produced in
flask-shaped structures containing nectar, which attract flies that transfer the spermatia to nearby hyphae for fertilization in a mechanism similar to insect pollination in flowering plants.[6] Fungal spermatia (also called pycniospores,
especially in the Uredinales) may be
confused with conidia. Conidia are spores that germinate independently of
fertilization, whereas spermatia are gametes that are required for fertilization. In some fungi, such as Neurospora crassa, spermatia are identical to microconidia as
they can perform both functions of
fertilization as well as giving rise to new organisms without fertilization.[7] Sperm nuclei In many land plants, including most gymnosperms and all angiosperms, the male gametophytes (pollen grains) are the primary mode of dispersal, for example via wind or insect pollination, eliminating the need for water to bridge the gap between
male and female. Each pollen grain
contains a spermatogenous (generative)
cell. Once the pollen lands on the stigma of a receptive flower, it germinates and
starts growing a pollen tube through the carpel. Before the tube reaches the ovule, the nucleus of the generative cell in the
pollen grain divides and gives rise to two
sperm nuclei which are then discharged
through the tube into the ovule for fertilization.[4] In some protists, fertilization also involves sperm nuclei, rather than cells, migrating toward the egg cell through a fertilization
tube. Oomycetes form sperm nuclei in a syncytical antheridium surrounding the egg cells. The sperm nuclei reach the eggs
through fertilization tubes, similar to the pollen tube mechanism in plants.[4] Sperm quality Human sperm stained for semen quality testing. Main article: Semen quality Sperm quantity and quality are the main parameters in semen quality, which is a measure of the ability of semen to accomplish fertilization. Thus, in humans, it is a measure of fertility in a man. The genetic quality of sperm, as well as its
volume and motility, all typically decrease with age.[8] (See paternal age effect.) Market for human sperm Further information: Sperm donation On the global market, Denmark has a well- developed system of human sperm export.
This success mainly comes from the
reputation of Danish sperm donors for being of high quality[9] and, in contrast with the law in the other Nordic countries,
gives donors the choice of being either
anonymous or non-anonymous to the receiving couple.[9] Furthermore, Nordic sperm donors tend to be tall and highly educated[10] and have altruistic motives for their donations,[10] partly due to the relatively low monetary compensation in
Nordic countries. More than 50 countries
worldwide are importers of Danish sperm,
including Paraguay, Canada, Kenya, and Hong Kong.[9] However, the Food and Drug Administration (FDA) of the US has banned import of any sperm, motivated by a risk
of mad cow disease, although such a risk is insignificant, since artificial insemination
is very different from the route of transmission of mad cow disease.[11] The prevalence of mad cow disease is one in a million, probably less for donors. If
prevalence was the case, the infectious
proteins would then have to cross the blood-testis barrier to make transmission possible.[11] Transmission of the disease by an insemination is approximately equal
to the risk of getting killed by lightning. [12] History See also: Homunculus#Homunculus of spermists Sperm were first observed in 1677 by Antonie van Leeuwenhoek [13] using a microscope, he described them as being animalcules (little animals), probably due to his belief in preformationism, which thought that each sperm contained a fully formed but small human.[citation needed] Forensic Analysis Ejaculated fluids are detected by ultraviolet light, irrespective of the structure or colour of the surface.[14] Sperm heads, e.g. from vaginal swabs, are
still detected by microscopy using the "Christmas Tree Stain" method, i.e.,
Kernechtrot-Picroindigocarmine (KPIC) staining

spermatids

The spermatid is the haploid male gametid that results from division of secondary spermatocytes. As a result of meiosis, each spermatid contains only half of the genetic
material present in the original primary
spermatocyte. Spermatids are connected together by
cytoplasmic material and have superfluous
cytoplasmic material around their nuclei. When formed, early round spermatids must
undergo further maturational events in
order to develop into spermatozoa, a process termed spermiogenesis (also termed spermeteliosis). The spermatids begin to grow a living
thread, develop a thickened mid-piece
where the mitochondria become localised, and form an acrosome. Spermatid DNA also undergoes packaging, becoming highly
condensed. The DNA is packaged firstly
with specific nuclear basic proteins, which
are subsequently replaced with protamines during spermatid elongation. The resultant
tightly packed chromatin is transcriptionally inactive.

SPERMATOGONIUM

A spermatogonium (plural: spermatogonia) is an intermediary male gametogonium (a kind of germ cell) in the production of spermatozoa. There are three subtypes: Type A(d) cells, with dark nuclei. These cells replicate to ensure a constant
supply of spermatogonia to fuel
spermatogenesis. Type A(p) cells, with pale nuclei. These cells divide by mitosis to produce Type B
cells. Type B cells, which divide to give rise to primary spermatocytes. Each primary spermatocyte duplicates its
DNA and subsequently undergoes meiosis I to produce two haploid secondary
spermatocytes. Each of the two secondary
spermatocytes further undergo meiosis II
to produce two spermatids (haploid). (1
primary spermatocyte => 4 spermatids) The spermatids then undergo spermiogenesis to produce spermatozoa.

URINARY SYSTEM

The urinary system (also called the excretory system ) is the organ system that produces, stores, and eliminates urine. In humans it includes two kidneys, two ureters, the bladder and the urethra. Physiology of urinary system Kidney Main article: Kidney The kidneys are bean-shaped organs that
lie in the abdomen, retroperitoneal to the organs of digestion, around or just below
the ribcage and close to the lumbar spine. The organ is about the size of a human fist
and is surrounded by what is called Peri-
nephric fat, and situated on the superior
pole of each kidney is an adrenal gland. The kidneys receive their blood supply of 1.25 L/min (25% of the cardiac output) from the renal arteries which are fed by
the abdominal aorta. This is important because the kidneys' main role is to filter water soluble waste products from the blood. The other attachment of the kidneys
are at their functional endpoints the ureters, which lies more medial and runs down to the trigone of urinary bladder. The kidneys perform a number of tasks, such as: concentrating urine, regulating electrolytes, and maintaining acid-base homeostasis. The kidney excretes and re- absorbs electrolytes (e.g. sodium, potassium and calcium) under the influence of local and systemic hormones. pH balance is regulated by the excretion of bound acids and ammonium ions. In addition, they remove urea, a nitrogenous waste product from the metabolism of amino acids. The end point is a hyperosmolar solution carrying waste for storage in the
bladder prior to urination. Humans produce about 2.9 litres of urine over 24 hours, although this amount may
vary according to circumstances. Because
the rate of filtration at the kidney is proportional to the glomerular filtration rate, which is in turn related to the blood flow through the kidney, changes in body
fluid status can affect kidney function.
Hormones exogenous and endogenous to
the kidney alter the amount of blood flowing through the glomerulus. Some medications interfere directly or indirectly with urine production. Diuretics achieve this by altering the amount of absorbed or
excreted electrolytes or osmalites, which causes a diuresis.

DIAPHRAGM

In the anatomy of mammals, the thoracic diaphragm, or simply the diaphragm (Ancient Greek: διάφραγμα diáphragma "partition"), is a sheet of internal skeletal muscle[2] that extends across the bottom of the rib cage. The diaphragm separates the thoracic cavity (heart, lungs & ribs) from the abdominal cavity and performs an important function in respiration. A diaphragm in anatomy can refer to other flat structures such as the urogenital diaphragm or pelvic diaphragm, but "the diaphragm" generally refers to the thoracic
diaphragm. Other vertebrates such as amphibians and reptiles have diaphragms or diaphragm-like structures, but important
details of the anatomy vary, such as the
position of lungs in the abdominal cavity. Function The diaphragm functions in breathing. During inhalation, the diaphragm contracts,
thus enlarging the thoracic cavity (the external intercostal muscles also participate in this enlargement). This
reduces intra-thoracic pressure: In other
words, enlarging the cavity creates suction
that draws air into the lungs. Cavity expansion happens in two
extremes, along with intermediary forms.
When the lower ribs are stabilized and the
central tendon of the diaphragm is mobile,
a contraction brings the insertion (central
tendon) towards the origins and pushes the lower cavity towards the pelvis,
allowing the thoracic cavity to expand
downward. This is often called belly breathing. When the central tendon is stabilized and the lower ribs are mobile, a
contraction lifts the origins (ribs) up
towards the insertion (central tendon)
which works in conjunction with other
muscles to allow the ribs to slide and the
thoracic cavity to expand laterally and upwards. When the diaphragm relaxes, air is exhaled
by elastic recoil of the lung and the tissues
lining the thoracic cavity. Assisting this
function with muscular effort (called forced exhalation) involves the internal intercostal muscles used in conjunction with the abdominal muscles, which act as an antagonist paired with the diaphragm's contraction. The diaphragm is also involved in non-
respiratory functions, helping to expel vomit, feces, and urine from the body by increasing intra-abdominal pressure, and
preventing acid reflux by exerting pressure on the esophagus as it passes through the esophageal hiatus. In some non-human animals, the
diaphragm is not crucial for breathing; a
cow, for instance, can survive fairly
asymptomatically with diaphragmatic
paralysis as long as no massive aerobic
metabolic demands are made of it. Anatomy The diaphragm is a dome-shaped
musculofibrous septum that separates the
thoracic from the abdominal cavity, its
convex upper surface forming the floor of
the former, and its concave under surface
forming the roof of the latter. Its peripheral part consists of muscular fibers
that take origin from the circumference of
the inferior thoracic aperture and converge to be inserted into a central tendon.

ADRENAL GLAND

In mammals, the adrenal glands (also known as suprarenal glands) are endocrine glands that sit atop the kidneys; in humans, the right suprarenal gland is
triangular shaped, while the left suprarenal
gland is semilunar shaped. They are chiefly
responsible for releasing hormones in response to stress through the synthesis of corticosteroids such as cortisol and catecholamines such as epinephrine. The adrenal glands affect kidney function
through the secretion of aldosterone, a hormone involved in regulating the osmolarity of blood plasma. Anatomy and Physiology Anatomically, the adrenal glands are
located in the retroperitoneum situated atop the kidneys, one on each side. They are surrounded by an adipose capsule and renal fascia. In humans, the adrenal glands are found at the level of the 12th thoracic vertebra. Each adrenal gland has two distinct structures, the adrenal cortex and the medulla, both of which produce hormones. The cortex mainly produces cortisol, aldosterone and androgens, while the medulla chiefly produces epinephrine and norepinephrine. The combined weight of the adrenal glands in an adult human ranges from 7 to 10 grams.[1] A CT scan in which the Adrenals are shown as the triangular-shaped organs on top of the kidneys Cortex The adrenal cortex is devoted to the synthesis of corticosteroid hormones. Specific cortical cells produce particular
hormones including cortisol, corticosterone, androgens such as testosterone, and aldosterone. Under normal unstressed conditions, the human adrenal glands
produce the equivalent of 35–40 mg of cortisone acetate per day.[2] In contrast to the direct innervation of the medulla, the
cortex is regulated by neuroendocrine hormones secreted by the pituitary gland and hypothalamus, as well as by the renin- angiotensin system. The adrenal cortex comprises three zones,
or layers. This anatomic zonation can be
appreciated at the microscopic level,
where each zone can be recognized and
distinguished from one another based on structural and anatomic characteristics.[3] The adrenal cortex exhibits functional
zonation as well: by virtue of the
characteristic enzymes present in each
zone, the zones produce and secrete distinct hormones.[3] Zona glomerulosa (outer) The outermost layer, the zona glomerulosa is the main site for production of mineralocorticoids, mainly aldosterone, which is largely responsible for the long-term regulation of blood pressure. Zona fasciculata Situated between the glomerulosa and
reticularis, the zona fasciculata is responsible for producing glucocorticoids, chiefly cortisol in humans. The zona fasciculata secretes a
basal level of cortisol but can also
produce bursts of the hormone in
response to adrenocorticotropic hormone (ACTH) from the anterior pituitary. Zona reticularis The inner most cortical layer, the zona reticularis produces androgens, mainly dehydroepiandrosterone (DHEA) and DHEA sulfate (DHEA-S) in humans. Medulla The adrenal medulla is the core of the adrenal gland, and is surrounded by the
adrenal cortex. The chromaffin cells of the medulla, named for their characteristic
brown staining with chromic acid salts, are the body's main source of the circulating catecholamines adrenaline (epinephrine) and noradrenaline (norepinephrine). Derived from the amino acid tyrosine, these water-soluble hormones are major
hormones underlying the fight-or-flight response. To carry out its part of this response, the
adrenal medulla receives input from the sympathetic nervous system through preganglionic fibers originating in the thoracic spinal cord from T5–T11.[4] Because it is innervated by preganglionic
nerve fibers, the adrenal medulla can be
considered as a specialized sympathetic ganglion.[4] Unlike other sympathetic ganglia, however, the adrenal medulla
lacks distinct synapses and releases its
secretions directly into the blood. Cortisol also promotes epinephrine
synthesis in the medulla. Produced in the
cortex, cortisol reaches the adrenal medulla
and at high levels, the hormone can
promote the upregulation of phenylethanolamine N-methyltransferase (PNMT), thereby increasing epinephrine synthesis and secretion.[3] Blood supply Although variations of the blood supply to
the adrenal glands (and indeed the kidneys
themselves) are common, there are usually
three arteries that supply each adrenal
gland: The superior suprarenal artery is provided by the inferior phrenic artery The middle suprarenal artery is provided by the abdominal aorta The inferior suprarenal artery is provided by the renal artery Venous drainage of the adrenal glands is achieved via the suprarenal veins: The right suprarenal vein drains into the inferior vena cava The left suprarenal vein drains into the left renal vein or the left inferior phrenic vein. The suprarenal veins may form anastomoses with the inferior phrenic veins. Since the right supra-renal vein is short and drains directly into the inferior
vena cava it is likely to injure the latter
during removal of right adrenal for various
reasons. The adrenal glands and the thyroid gland are the organs that have the greatest blood
supply per gram of tissue. Up to 60 arterioles may enter each adrenal gland.[5] This may be one of the reasons lung cancer
commonly metastasizes to the adrenals. Terminology The adrenal glands are named for their
location relative to the kidneys. The term
"adrenal" comes from ad- (Latin, "near")
and renes (Latin, "kidney"). Similarly,
"suprarenal" is derived from supra- (Latin,
"above") and renes.

INFERIOR VENA CAVA

The inferior vena cava (or IVC), also known as the posterior vena cava,[1] is the large vein that carries de-oxygenated blood from the lower half of the body into the right atrium of the heart. It is posterior to the abdominal cavity and runs alongside of the vertebral column on its right side (i.e. it is a retroperitoneal structure). It enters the right atrium at the lower right, back side of the heart. Drainage patterns The IVC is formed by the joining of the left
and right common iliac veins and brings blood into the right atrium of the heart. It also anastomoses with the azygos vein system (which runs on the right side of the
vertebral column) and venous plexuses next to the spinal cord. The caval opening is at T8. The specific levels of the tributaries are as follows: Vein Level hepatic veins T8 inferior phrenic vein T8 suprarenal vein L1 renal veins L1 gonadal vein L2 lumbar veins L1-L5 common iliac veins L5 Because the IVC is not centrally located,
there are some asymmetries in drainage
patterns. The gonadal veins and suprarenal veins drain into the IVC on the right side, but into the renal vein on the left side, which in turn drains into the IVC. By
contrast, all the lumbar veins and hepatic veins usually drain directly into the IVC. The tributaries of Inferior vena cava can be
remembered using the mnemonic, "I Like To Rise So High", for Illiac vein (common), Lumbar vein, Testicular vein, Renal vein, Suprarenal vein and Hepatic vein.[2] Note that the vein that carries de-
oxygenated blood from the upper half of
the body is the superior vena cava . Pathologies associated with the IVC Health problems attributed to the IVC are
most often associated with it being
compressed (ruptures are rare because it
has a low intraluminal pressure). Typical sources of external pressure are an
enlarged aorta (abdominal aortic aneurysm), the gravid uterus (aortocaval compression syndrome) and abdominal maligancies, such as colorectal cancer, renal cell carcinoma and ovarian cancer. Since the inferior vena cava is primarily a
right-sided structure, unconscious pregnant
females should be turned on to their left
side (the recovery position ), to relieve pressure on it and facilitate venous return.
In rare cases, straining associated with defecation can lead to restricted blood flow through the IVC and result in syncope (fainting).[3] Occlusion of the IVC is rare, but considered
life-threatening and is an emergency. It is
associated with deep vein thrombosis, IVC filters, liver transplantation and instrumentation (e.g. catheter in the femoral vein).[4] Embryology In the embryo, the IVC and right atrium are separated by the Eustachian valve , also known in Latin as the valvula venae cavae inferioris (valve of the inferior vena cava).
In the adult, this structure typically has
totally regressed or remains as a small endocardial fold.