Male Reproductive System

Accessory sex glands

• Seminal vesicles
• Secrete thick alkaline fluid
• Bulbourethral (Cowper’s) glands
• Add fluids to semen 
• Prostate gland
• Secrete thin milky fluid

Ducts

• Epididymis
• Nutrition to sperms, become motile
• Vas deferens
• Continuation of tail of epididymis, secondary storage for sperms
• Ejaculatory ducts
• Union of ducts of vas deferens and seminal vesicles, opens into prostatic urethra
• Urethra
• Male urethra – muscular tube of 18 to 20 cm, conveys urine from internal sphincter to external sphincter
• Also exit for semen (sperms & glandular secretions)

Supporting structures

• Spermatic cord
• Suspend testis in scrotum,  contains vas deferens, vessels & nerves of testis – pass through inguinal canal
• Scrotum
• Cuteneous fibromuscular sac
• Houses testis, epididymis and lower end of spermatic cord
• Maintains temperature lower than body, necessary for spermatogenesis
• Penis
• Male copulatory organ, common outlet for urine & semen

Gonads

• Pair of testis - Ovoid bodies suspended by spermatic cords into scrotum
• Weighs - 25 g
• 3 layers
1. Tunica vasculosa (innermost)
2. Tunica albuginea (middle)
3. Tunica vaginalis (outermost)

Blood supply

• Artery – Testicular artery, Br. of abdominal aorta
• Vein – Pampiniform plexus of veins
• Lymph nodes – Lumbar & Pre-aortic nodes
• Nerve – Testicular plexus
• Testis is divided into many lobules by fibrous septa
• Lobules contain 2 compartments
1. Seminiferous tubular compartment
2. Intestitial compartment

Seminiferous tubular compartment

• Forms 80-90% of testicular volume
• Contains seminiferous tubules, which has two parts
1. Convoluted part
2. Straight part
• Terminal straight part is called rete testis and is continuous with epididymis

Histology of seminiferous tubules

• 3 layers
1. Tunica propria
2. Basement membrane
3. Epithelial layer
• Germ cells (Spermatogenic cells)
• Supporting cells or sustenticular cells (Sertoli cells)

Sertoli cells

• Physical support & nutrition to maturing germ cells
• Phagocytic function
• Maintenance of blood-testis barrier
• Secretory function
• Mullerian duct inhibitory substance (MIS)
• Inhibin
• Androgen-binding protein
• Oestrogen
• Transport proteins
• Plasminogen activator
• Seminiferous tubular luminar fluid

Interstitial compartment

• Forms 10-20% of testicular volume
• Filled by loose connective tissue & Leydig cells
• Leydig cells have endocrine function of secretion of male sex hormone – testosterone

Functions of Testis

1. Gametogenic function (Spermatogenesis)
2. Endocrine function

Spermatogenesis

• Process of formation of spermatozoa from the primitive germ cells (spermatogonia)
• Average duration – 74 days
• At 32 deg. C
• Occurs in 4 stages
1. Stage of proliferation
2. Stage of growth
3. Stage of maturation
4. Stage of transformation

Phases of spermatogenesis

Phase of mitotic division of spermatogonia

1à2à4à8à16à32

Phase of formation of primary spermatocytes by mitotic division

32 (44+X+Y) x 2 = 64 (44+X+Y)

Phase of formation of secondary speramatocyte by meiotic division

64 (n) x2 = 128 (n) & 128 (n) x 2 = 256 (22+X or 22+Y)

Phase of formation of spermatid

256 (n) x 2 = 512 (n)

Phase of formation of spermatozoon

No further division, undergoes changes in shape and orientation of its organelles

Semen

• Fluid ejaculated from male genital tract during orgasm
• Contains sperm, seminal fluid & secretion from prostate & bulbo-urethral gland
• Volume: 2.5ml - 3.5ml/ejaculation
• Colour - White opalescent
• Specific Gravity =1028
• pH=7.35-7.50
• Sperm count = 80 to100 million/ml

Endocrine function of testis

• Leydig cells – male sex hormones – androgens
• Sertoli cells – oestrogen, inhibin & activin
• Andrognes
• Testosterone
• Androsternedione
• Dihydrotestosterone

Functions of androgens

• Fetal period
• Sex differentiation in fetus and descent of testes
• Puberty
• External genitalia – pigmentation & enlargement
• Accessory sex organs - enlargement of seminal vesicles and growth of prostrate
• Development of male secondary sexual characters
• Psyche - male pattern of sexual behavior, initiates sexual drive
• Anabolic & growth promoting effects
• Nitrogen retention - rapid increase in stature
• Adults
• Hair growth – male pattern & baldness
• Psyche – behavioral attitudes & sexual potency
• Bone loss & osteoporosis prevented
• Speramtogeneisis
• Haematopoiesis
• Increases circulating levels of LDL
• Regulation of gonadotropin secretion

Applied Aspects

Hypergonadism

• Excessive secretion of male sex hormones – tumours of leydig cells
• Charecterised by
• Rapid growth of musculature of bones
• Height is less due to early closure of epiphysis
• Excessive development of sex organs and secondary sexual characters at an early age
• Overgrowth of breasts (Gynaecomastia)

Regulation of water, electrolyte and acid-base balance

Regulation of Water Balance 

• The Glomerular Filtration Rate (GFR) of all the nephrons of both kidneys is 125 ml/min. or 180L/day
• That is 125 ml of blood is filtered each minute or 180 L of blood is filtered each day.
• Daily urine output is 1-1.5 L/day.
• That means more than 99% of glomerular filtrate is absorbed normally.
• Water reabsorption occurs passively by diffusing along an osmotic difference established by the reabsorption of Na+ and Cl-

Water reabsorption

• Reabsorption from PCT (Obligatiory water reabsorption)
• 60-70% reabsorption occurs due to osmotic difference set by active transport of solutes
• Reabsorption from Loop of Henle
• 5-10% reabsorption occurs here.
• Reabsorption from DCT and CT
• In early part of DCT 5-8% reabsorption occurs secondary to reabsorption of Na+ under the influence of aldosterone.
• In the terminal DCT and CT (Facultative water reabsorption)  reabsorption of 10-12% by the action of ADH hormone.

Regulation of Electrolyte balance

• The concentration of solute in urine varies widely
• In overhydration where there is excess of water, kidneys excrete dilute urine
• In dehydrateion where there is less water, kidneys excrete concentrated urine
• The process involved in excretion of concentrated or diluted urine are
• Variable permeability of the nephron to different solutes
• Passive reabsorption of NaCl by the thin segment of ascending loop of Henle
• Active reabsorption of Na by thich segment of ascending loop of Henle

Kidneys regulate the concentration of water and electrolyte (NaCl) in the blood and thus regulate the blood pressure.

• The mechanism involved in this process is Renin-Angiotensin-Aldosterone system

 

 Acidification of urine

• Our body produces H+ ions during various metabolic process. 
• The H+ ions produced has to be excreted to maintain electrical neutrality in the body.
• Kidneys play an important role in excretion of H+ ions through urine.
• As H+ ions are excreted in urine, the normal urine is acidic in nature (increase in H+ ion concentration)

How do kidneys excrete H+ ions?

The acidification urine or excretion of H+ ions occurs in Distal Convoluted Tubule and Collecting duct of Renal tubule.

The H+ ions excreted in the urine is entirely by process of secretion by the tubular cells.

There are three systems through which H+ ions are excreted

1. Bicarbonate system
2. Dibasic phosphate system
3. Ammonia system

Bicarbonate system

Dibasic phosphate system

Ammonia system

The H+ ions are excreted in combination with the buffer systems, which are

• with bicarbonate as carbonic acid
• with hydrogen phosphate a dihydrogen phosphate
• with ammonia as ammonium ion

Application and Implication in Nursing

Glomerulonephritis

• Inflammation of the glomerulus is called glomerulonephritis. It is caused by antigen-antibody complex.

Pyelonephritis

It is an acute infection of kideny, pelvis and calyces by microorganisms.

It is associated with

• Abscess fomation
• Fever
• Malaise
• Groin pain 
• Burning micturition.

The source of infection may be the uriniary tract or blood-borne.

Nephrotic Syndrome

It is a collection of symptoms which are

• Albuminuria: Albumin lost in urine
• Hypoproteinaemia: Decrease in plasma protein level
• Generalized oedema: Abnormal collection of fluid in intestinal spaces
• Hyperlipidaemia

 

Skin, Smell, Taste

Our brain receives sensory nformation from the environment through 5 special sensations. They are

1. Touch
2. Smell
3. Taste
4. Hearing 
5. Vision

 Skin 

• Skin is the outermost covering of the body.
• The sensation of touch is subserved by the skin.
• It is the largest organ in the body.
• Skin contains glands, hair, nails and 2 layers, which are:
• Epidermis 
• Dermis

Epidermis

It is made of stratified squamous epithelium.

It has 5 layers

1. Stratum corneum
2. Stratum lucidum
3. Stratum granulosum
4. Stratum spinosum
5. Stratum germinatium

Stratum germinatium contains melanocytes which synthesise a pigment called melanin which is responsible for the colour of the skin.

Dermis

It is made of connective tissue.

Hairs

They arises from the hair follicles.

They are attached to erector pilae muscle.

During sympathetic stimulation like fear, excitement, exposure to cold etc. the hair stands erect.

Glands

Two types of glands are present in the skin

1. Sabeceous glands which secrete oily sebum
2. Sweat glands are of 2 types
1. Aporice sweat glands presnet in axilla, genital area and around nipple
2. Eccrine sweat glands which are responsible for heat regulatory mechanism.

 Functions of the skin 

1) Protective function

• Melanin pigment absorbs ultraviolet rays and prevents the tissue damage by ultraviolet radiation.
• Skin acts as a barrier to invasion of harmful agents like bacteria and toxic chemicals.

2) Sense perception

• The receptors present in the the skin helps in sensory perception.

3) Temperature regulation

• Skin helps in dissipiation of heat from the body by conduction, convection & radiation there by helping the regulation of temperature in the body.

4) Water balance

• Skin doesnot allow large amount of water to pass through it this helping the water balance of the body.

5) Elimination

• Substance such as urea is excreted in sweat though the skin.

 Smell 

• The sense of smell is called olfaction.
• The receptors for smell are olfactory receptors which are present in the roof of the nasal cavity.

Olfactory pathway

Olfactory receptors

↓

Through Cribriform plate

↓

Olfactory bulb

↓

Second order neurons project on to olfactory area in the sensory cortex

Olfactory pathway

Unique feature of olfaction

• Humans can differentiation 2000 to 4000 different smells
• Olfactory receptors are highly adaptable which is known as olfactory fatigue.
• Smell pathway do not relay in the thalamus unlike other sensations.

Application & Implication in Nursing

• Anosmia – loss of sense of smell
• Hyposmia – reduced ability to smell

 Taste 

The sensation of taste is known as Gustation.

The receptors for taste sensation are chemoreceptors present on the tongue, glottis, soft palate & pharynx.

The taste buds are embedded in papillae present on the the surface of tongue.

There are 4 types of papillae

1. Fungiform papillae
2. Filiform papillae
3. Circumvillate papillae
4. Foliate papillae

In humans there are about 10,000 taste buds which decline after age.

Taste buds

They are oval shaped cluster of cells containing gustatory receptors cells & sustenticular/supporting/basal cells.

Structure of Taste bud

Taste pathway

Taste pathway

Anterior 2/3rd from 7th cranial nerve and Posterior 1/3rd from 9th and 10th cranial nerve

↓

Medulla

↓

Post central gyrus (Sensory cortex)

Types of taste sensations

1. Sweet
2. Salt
3. Sour
4. Bitter
5. Umami

Types of taste sensations

Application & Implication in Nursing

• Flavour: it is a complex sensation consisting of taste, odour, roughness/smoothness, hotness/coldness, pungent/blandness.
• Aguesia: Complete loss of taste sensation
• Dysgeusia: Partial loss of taste sensation

Disorders of taste sensation are seen in salivary gland infections, sinusitis, poor dental hygiene.

Spinal cord, CSF & Blood Brain Barrier

Spinal cord

• Long narrow cylindrical structure located in the vertebral canal.
• Begins from the base of the skull at formane magnum and terminate at the lower border of first lumbar vertebra
• Below the first lumbar vertebra it continues as cauda equina (Horse tail)

Cross section

• Anterior median fissure
• Posterior median fissure
• Central canal

H shaped grey matter with anterior horn containing motor neurons and posterior horn containing sensory neurons

Surrounding the grey matter is white matter consisting of ascending and descending tracts. 

*Grey matter consists of cell bodies and white matter consists of axons.

The arrangement of grey and white matter in brain and spinal cord is different. In the brainstem and spinal cord white matter surrounds the grey matter while in cerebrum and cerebellum, it is the grey matter which surrounds the white matter. The fatty myelin on the myelinated nerve gives its white appearance and the cell bodies have grey appearance.

Cross section of Spinal cord

There are 31 pairs of spinal nerves

• 8 pairs of cervical nerves
• 12 pairs of thorasic nerves
• 5 pairs of lumbar nerves
• 5 pairs of sacral nerves
• 1 pair of coccygeal nerve

Cerebrospinal Fluid (CSF)

Brain and spinal cord is covered by 3 meninges: dura, arachnoid and pia matter. 

The space between the arachnoid and pia matter contains a fluid known as Cerebrospinal Fluid.

The CSF is also present in the chambers of the brain called ventricles namely lateral, third and fourth ventricle.

Composition of Cerebrospinal Fluid

• Clear colourless 
• Alkaline (pH>7)
• Specific gravity: 1.005-1.008
• Protein and cell free
• Volume: 130-150 ml
• Daily secretion: 500 to 550 ml
• Pressure: 130 mm of water

Formation of Cerebrospinal Fluid

• 50% by choroid plexuses
• 40% by blood vessels of th emeningeal and ependymal lining of ventricles
• 10% by blood vessels of brain and spinal cord.

Flow of Cerebrospinal Fluid

Functions of Cerebrospinal Fluid

• It serves as a fluid buffer providing an optimum environment to the neurons.
• Protective function: It supports the brain by cushioning. The brain actually floats in CSF.
• It keeps the total volume of cranial content constant.
• It helps in transfer of waste products of brain into the blood.
• It serves as a medium for nutrient exchanges in the nervous system.

Blood Brain Barrier

It is the barrier between the blood and the brain tissue.

It is present in two places with in the brain

1. One is located at the interface of Choroid plexus and CSF, called Blood CSF barrier.
2. Second one is located between Brain capillaries and CSF, called true Blood Brain Barrier.

These barriers are:

• Highly permeable to water, oxygen, carbondioxide and sulpha drugs.
• Slightly permeable to electrolytes and glucose.
• Impermeable to metal, urea, protein and bile salts.

Functions of Blood Brain Barrier

• They help in maintanace of constancy in the CNS environment.
• They protect the brain from endogenous and exogenous toxins in the blood.
• They prevent escape of neurotransmitters into the circulation.

Cerebrum, Limbic system

Central Nervous System

The part of the nervous system which occupies the central axis of the body is known as Central Nervous System

It comprises of brain and the spinal cord

Brain

It weighs about 1.5 kg in adults and consists of all the structures which are intracranial (located within a hard bony skull)

It is completely surrounded by three membranes which are called the meninges. From outside to inwards the meninges are:

1. Dura mater
2. Arachnoid mater
3. Pia mater

The brain consists of the following parts

1. Two cerebral hemispheres (cerebrum)
2. Brain stem (medulla, pons, midbrain)
3. Cerebellum

Cerebrum

It is the largest part of the brain and is divided into the right and left cerebral hemispheres.

The two cerebral hemispheres are separated by a space in which the falx cerebri (dura mater) invaginates.

The two hemispheres are connected to each other by a bundle of nerve fibres called the corpus callosum.

The most superficial part of each cerebral a hemisphere is called the cerebral cortex (cerebral grey matter) and it is 2-4 mm thick.

Its total surface area is 2,200 cm2 

Underneath the cerebral cortex lies the subcortical white matter in which are located masses of the grey matter called the subcortical nuclear mass such as the basal ganglia, thalamus and hypothalamus.

These nuclear masses consist of nerve cells (soma), packed up very densely together with their axons and dendrites.

Each cerebral hemisphere has three poles: frontal pole, temporal pole and occipital pole.

The entire cerebral hemisphere is marked by elevations called gyri and depressions called sulci, which give a characteristic appearance to it.

 

The important sulci are:

1. Central sulcus: It runs from the superiomeidal border midway between midpoint of the occipital and the frontal pole
2. Lateral sulcus: It lies between the frontal and the temporal pole
3. Parieto-occipital sulcus

With reference to these major sulci, the whole of the cerebral hemisphere is divided into four lobes, which are concerned with higher mental functions:

1) Frontal lobe:

• It lies in front of the central sulcus and is concerned with motor functions, Contraction. Located in front of the frontal muscle i,e,, initiation and control of voluntary lobe is the prefrontal lobe. It is concerned with the control of higher intellectual activities, emotional affects, behaviour and social consciousness, personality, memory, sense of responsibility, thinking, reasoning, moral sense and learning, etc.

(ii) Parietal lobe:

• It lies between the central sulcus and the parieto-occipital sulcus. It is concerned with sensory functions such as the following:
• It is concerned with appreciation of the elementary sensations of touch, pain, pressure, temperature (heat and cold) and joint movements
• It is associated with a more detailed process of discrimination between the stimuli. Therefore, warm objects are distinguished from warmer, cold from colder and rough from rougher, etc.
• It helps in the recognition of common familiar objects placed in the hand without looking at them (stereognosis).

(iii) Occipital lobe: 

• It lies behind the parieto-occipital sulcus and is concerned with vision.

(iv) Temporal lobe: 

• It lies below the lateral sulcus and is concerned with hearing, language (speech) and memory functions. 8. In addition, there is a limbic lobe (i.e., cingulate gyros, hippocampus) in the temporal lobe. Limbos means a ring and the term limbic system is applied to the parts of the cortical and subcortical structures that form a ring around the brain stem. The limbic cortex is phylogenetically the oldest pan of the cerebral cortex. Histologically, it is madE up of a primitive type of cortical tissue callk allocortex.

Functions of the Limbic System

• The limbic system represents the primary area of control of autonomic functions.
• It plays an important role in
• the emotions of rage (violent anger) and fear; and
• the motivation.
• It is concerned with the behavioural aspects of hunger and sex.
• It is also concerned with olfaction and memory.

Brodmann divided each of the cerebral hemispheres into several areas called Brodmann areas. Each cerebral hemisphere contains a total of 47 such functional areas, thinking that each area has an absolutely selective function.

The typical cortex contains six layers, numbered I to VI, from the outside to the inside.

Adrenal Cortex

 The adrenal glands sits at the top of Kidney, hence they are called suprarenal glands

There are 2 adrenal glands, one on each kidneys

The adrenal glands has two parts: outer adrenal cortex and inner adrenal medulla

Adrenal cortex secretes steroid hormones and adrenal medulla secretes catecholamines

Adrenal glands are essential for life

Adrenal cortex has three layers:

1. Zona glomerulosa which secrete mineralocorticoids, eg: aldosterone
2. Zona fasciculata which secret glucocorticoids, eg: cortisol
3. Zona reticularis which secrete sex steroids, eg: androgen, oestrogen and progesterone.

Adrenal medulla secretes:

• Epinephrine
• Nor-epinephrine
• Dopamine

Regulation of glucocorticoid secretion is done by ACTH (Adrenocorticotrophic Hormone)

• Hypothalamus release CRH (Corticotropin Releasing Hormone) which stimulates anterior pituitary to secrete ACTH via hypothalamo-hypophysial portal system

Factors affecting ACTH secretion

• Diurnal variation of ACTH secretion/circadian rhythm
• Response to stress

Actions of Glucocorticoids

On protein metabolism

• Causes breakdown of proteins in skeletal muscles

On carbohydrate metabolism

• Increases glucose fomation in the liver
• Prevent peripheral utilization of glucose causing increase in blood glucose level
• Increases glycogen synthesis

On fat metabolism

• Favours mobilization of fatty acids from adipose tissue

On electrolyte and water metabolism

• Increases retention of sodium and excretion of potassium by kidneys

Vascular reactivity

• Sensitizes arterioles to constrictor actions of catecholamines
• Maintains blood pressure

Anti-inflammatory and Anti-allergic action

High doses causes

• Decreased local reaction
• Prevents tissue damage
• Decreased fibroblastic activity
• Reduces histamine induced features of allergy

Cushing’s syndrome

It is a clinical disorder which results from excess secretion of glucocorticoids

Characteristic features

• Growth retardation in childhood due to early fusion of epiphysis
• Facial features: Moon like face, Hirsutism, Acne & pigmentation
• Centripetal distribution of fat: Thin extremity, pendular abdomen, Buffalo hump
• Purple striae due to thinning and stretching of skin

Actions of Mineralocorticoids (Aldosterone)

• Causes retention of sodium and increased urinary excretion of potassium
• By stimulating sodium reabsorption, aldosterone causes water retention resulting in expansion of extracellular fluid volume

Regulation of aldosterone secretion

• Decrease in plasma sodium increases aldosterone secretion via renin-angiotensin-aldosterone system
• Circadian rhythm

Applied Aspects: Addison’s disease

• Decrease in secretion of mineralocorticoids leads to Addison’s disease

Symptoms are:

• Hypotension
• Anorexia, nausea, vomiting, diarrhea leading to dehydration and weight loss
• Muscular weakness, mental confusion
• Decreased ability to withstand stress due to trauma, infection

Sex hormones

• At puberty adrenal glands secrete sex hormones, testosterone in males, estrogen and progesterone in females
• It contributes to increase in the muscle mass, sexual hair, pimples etc.
• It secretion is regulated by ACTH

Introduction to Endocrine System

Cellular functions are controlled by two mechanism:

• Neural control mechanism
• Endocrine control mechanism

Neural vs Endocrine System

Neural control mechanism involves the nerves through which impulses are transmitted to certain group of cells to control its function. The action is rapid and short lived.

Endocrine control system involves hormones which are secreted directly into the blood stream and controls the function of number of cells. The action is show and long lived.

The hormones are secreted into the bloodstream by ductless glands called Endocrine glands.

Important endocrine glands are

• The hypothalamus
• The Anterior pituitary (Adenohypophysis)
• The Posterior pituitary (Neurohypophysis)
• The islets of Langerhans in the Pancreas
• The Adrenal cortex
• The Adrenal medulla
• The Thyroid
• The Parathyroid
• The Kidney
• The Ovary and the Testis

Endocrine Glands

Definition of a hormone

Hormones are secretory products of ductless (endocrine) glands released directly into the circulation in small amounts in response to a specific stimulus and on delivery in circulation produce response on the target cells or organs.

Characteristics of a Hormone

Hormones interact with the target cells via receptors which are large protein molecules.

Hormones bind to receptor to form a hormone receptor complex which through second messenger system controls the functions of target cells.

The second messenger systems are:

1. Cyclic Adenosine Mono-Phosphate (cAMP)
2. Cyclic Guanosine Mono-Phosphate (cGMP)
3. Inositol Triphosphate (IP3)
4. Calcium Calmodulin
5. Tyrosine Kinase

Second messenger system

Hormones regulate the body process, but will not initiate the cellular reactions

Hormones as a regulator controls the functions of target cells by controlling the enzymes.

Hormones are metabolized rapidly and inactivated by liver and kidney

Application and implication in Nursing

Q. What are the common symptoms found in the most of the endocrine disorders?

A. 

• Fatigue and weakness
• Weight changes
• Blood glucose level fluctuation
• Abnormal cholesterol level
• Mood changes